I would definitely go with Yoga. Good isometric exercise, helps with balance, posture, increases energy flow, boosts your immune system, maximizes weight loss, maximizes muscle growth. Make sure to add some form of mindfulness meditation (attention to breath is easy and most effective). Check YouTube for latest scientific evidence of mindfulness meditation benefits. It will blow your head off.
As for abs and core, don't get too fancy. Lots of unnecessary complication around. Stick to good ol' sit ups, and for isometrics, planches. But it is my opinion that simplefit's push up routine already gives you enough ab and core work. There is really no need to add more, unless you're going for the six-pack look. And in that case, losing fat is paramount, more than working the abs.