Mostly I write from the teacher's perspective, but if you work at a non-profit serving trauma survivors and would like to find a trauma informed yoga instructor for an ongoing class, what do you do?
Training for the teacher
The most obvious route to finding a yoga teacher may be to post an ad on Craigslist, or reach out at your local yoga studio, especially if you personally know and like a teacher. Trusting your gut is important, particularly if the teacher you know is also familiar with your clients and some common concerns, but most teachers do not receive training in trauma-informed yoga unless they seek it out.
You might approach yoga non-profits that offer such training in your area and ask them to put you in touch with their graduates. Often those who have sought out training have an internal motivation to do the sort of work they trained in - and this may translate into more of a commitment than someone who is doing a favor. You could also specifically mention experience with or training in trauma informed yoga any request or ad put out.
If your organization offers an orientation for "regular" (non-yoga teacher) volunteers, consider inviting your yoga teacher to attend an orientation too. Even though teaching yoga may differ from what other volunteers do, learning about some common client concerns can provide important insight for the teacher.
Consider the costs of a yoga class, for your organization and for the teacher. The space will be used for that time, you may need to invest time collecting donated mats (or purchase mats). The time the teacher spends teaching the class and commuting is time that they can't be teaching in other (paid) settings. If your organization requires yoga liability insurance, this usually costs a teacher more than $100/year, though they may well need it for other paid work too. Many motivated volunteers understand that funds are in short supply and may be willing to teach on a volunteer basis; if a stipend is available, or if you have trouble securing a volunteer instructor who can commit to a regular schedule, consider it.
Most yoga teachers, even those who work a "regular" job and teach part-time, manage a complex schedule. Before finding a teacher, consider what time would work well for your organization and clients, and share this with potential teachers right away in your search. A time when more clients will be able to attend (evenings if most have daytime jobs) and which is also not a busy time for your organization (too crowded to spare space) will probably be ideal. A teacher who isn't available at the times you seek can learn that at the start of the set up process (and decline) rather than after many phone calls, emails and visits.
Take the steps you can to make the yoga space as calming as possible. A teacher who has taken the initiative to do trauma-informed yoga training will likely have some information on creating a trauma-informed environment. If a private room is feasible, ensure the room can be reserved each class; if not, choose a section of the space with a minimum of disruptions, and ensure that other volunteers or clients give that space a wide berth. Determine which sounds in the room could be quieted (radio or tv could be turned off by staff for the duration of the yoga class) and take regular steps to do so. It's quite likely a yoga instructor won't feel s/he has the authority to ask staff members to do louder work elsewhere, or to ask non-practicing clients to keep their voices at a lower level - so either let everyone know the teacher is in charge, or take these steps yourself.
If the yoga instructor is not a staff member with your organization, have a staff member who can consistently take the class with the group, sit nearby, or just be available onsite during and around the class time. A second person and especially a staff member with a mental health background can be a tremendous help if a student decides to leave the class or has concerns or just needs help.
Promote the class to your clients. I never recommend mandatory (or even incentivized) participation, but avoid assuming that simply holding the class is enough to get people to come. A large group isn't necessary, but a small group is often nicer for everyone than one or two people...or of course none. Consider whether opening the class to the pubic (in the sense of other non-profits serving a similar group) would make sense in terms of building a regular group of participants. Some teachers promote yoga service classes they set up themselves; this can be a challenge if only clients of your organization can attend the class.
Work with the teacher to develop an accurate description of what participants can expect. "Practice yoga in bare feet or socks"..."participants should be comfortable sitting on the ground and rising up to standing; chairs are also available" ... depending on what the teacher can actually offer. Many yoga teachers would struggle to teach for 60 minutes without use of yoga mats or without participants using hand and feet on the ground. Some teachers are trained or can train in chair yoga; a chair yoga class might be better in a30 minute class. While sitting may seem less effortful than standing, a cross legged seat on the ground is often not comfortable for any sustained amount of time for many people. Standing poses may feel more attainable than seated poses if taken at a reasonable pace.
Figure out how you will inform clients if cancellations occur, or if the schedule changes. This may involve collecting info like email address or phone number in advance.
A lot of yoga teachers will need mats to teach; if not mats, chairs (and chairs can be great to have nearby to hold on to for balancing postures, or for people who don't feel comfortable at all sitting on the ground, even if some in the group do). You can work with the teacher to request donated mats. If you do collect mats, consider where they can be stored (securely, somewhere easy to access for the teacher each time they are needed) or transported (yoga mats are heavy even if the teacher has a car and nearby parking). If clients are likely to worry about removing their socks or shoes because they think their feet are unsightly, perhaps the organization can keep several pairs of new socks on hand. Lysol wipes are useful to keep on hand before and after class to wipe down mats.
Non-yoga teachers offering yoga
Can a staff member who is not a certified yoga teacher offer yoga? This is a big topic. Most people, even committed yoga students, would need quite a bit of training to gain the practical skills of teaching a class. That said, trauma-informed classes in non-profit spaces are often much slower paced and gentler than public yoga classes. Many social service professionals already integrate some yoga practices into their work.