The 2:30 thing with DS#1 is probably going to be an issue. If you can put him to bed earlier then I think that will solve a lot of problems. That's great he was able to do a 2 hour nap at noon! If he does that, then I'd have him in bed at 6:30, hoping that he'd fall asleep by 7. If you can get him to do that kind of routine that would really solve a lot of problems: you'd have him up well in time to pick up DS#1 and you'd be getting him in bed early enough that he wouldn't be OT at bedtime. Gosh, maybe you'll have a super easy 2-1 switch!
My guess is, tho, if you do manage to get him to do 1 nap some days he probably won't be able to handle it every day of the week. Still, if you could do 1 nap 2-3 days/week that would go a long way towards transitioning him. What do you think about trying that? I suppose it all depends on that AM waking. How likely is it that you can have him wake 7 or later?