I would suggest CMC 37 Step Taichi (Cheng Man Ching) I found it is suitable for or ''better for the elders'' folks. I have learned this style and found that the form does not require too much physical demand.
For ''better in stress'' reduction, I still recommend CMC 37 or Yang 47 performed at a slower pace.
But you need to check out the teacher as some are teaching it, the 2 style mentioned above, as a form of Martial Art or self-defenced.
The Sun and Wu are more martial art or self-defenced oriented.