Are the benefits of meditation and general stretching included in yoga and pilates?

Yes: If appropriately practiced, i would think so. Impossible to predict in a particular case, and even more, lacking serious scientific studies (...How to measure this accurately? How to replicate a study?) it is hard to guarantee it though. But no doubt, if your dr approves it, go ahead. It should be healthy and good for you. I admire your willingness to explore and analize good things ! congrats.