A beginning Iyengar class might be a good place to start because they tend to move slowly and focus a lot on alignment. While I love vinyasa classes, they move more quickly (one breath per pose for a good part of the class). I would go that route instead of restorative because what it sounds like you are looking for right now is more strength-building. A class that's labeled hatha might also work, but that's a bigger umbrella term. Wherever you start, look for a beginner class or series, where you can really learn the foundations.

Keep the lines of communication open with your physical therapist or doctor and ask them specifically anything you should avoid--pass this on to your teacher. It's a big red flag if the teacher tells you to push through pain or tells you to ignore the advice of your physical therapist. Most teachers out there, however, are very open to helping you work within your current framework.

In terms of your wife's asthma, I would also check out the studio because for some reason many yoga people are cat people which might aggravate her asthma. Some studio owners let their cats walk around the studio. I would prefer to see a wood floor, which traps less dander, and you want to check out or inquire about how often they wash their blankets and other props, which can collect a lot of dust. I suffer from very strong cat and to dust allergies and have had big flare ups in some studios. It's just something to look for before committing to a punch card or a class series.