As long as you're spending lots of time with him, he doesn't need anything else. Maybe lie on the floor with him and sing or tell stories...he loves your smell and your voice more than anything else on the planet. :)
As kiwispiers suggests, do try some tummy time. Mine all hated it so I never pushed it (and they are all fine :D ) but it is good for their development to spend some time on their tummy.
I think the most important thing is to recognise when he's had enough and the start your soothe to sleep routine [u'>before[/u'> he is actually tired. This avoids over-stimulation and helps in better, longer sleeps. :)
1)Tummy time, its not good for his motor development or head shape if he is lying on his back in the playgym the whole time.
2) Mummy time, spend a good part of that time cuddling him and talking to him, smiling etc at a close distance to his face.
Don't make him miserable trying to do the "right" thing though, figure out what works best for you and your baby. :)
2 hrs is normal. If he's content laying down, let him. There's not much to do or watch at this time which is the best! Get some work done or just Lay there with him :) enjoy it