Broms, not real advice but just lots and lots of sympathy here. DD is now 3.5 and is MUCH better now she is at pre-school for 5 mornings a week with lots of activities in the afternoons. The dark mornings also help because she is now old enough to understand that it is still night time. she wakes about 5ish at the moment but she climbs into bed with us and we go back to sleep.
You DS is probably too young for this but before 6AM I basically tell her it is still night time and if she wants to be awake that is fine but there will be no lights on, no talking and no TV. The minute she tries to talk she is back in her room. For the last week she has gone back to sleep until about 6.30. Although this wouldn't have worked a year ago because she would have just screamed at me until I gave in.
I did find an earlier bedtime helped. She also got better when she cut out her naps but as you say, when they have been up since 4AM there is no way you can do no naps.
I know you say that your DS is really active but the other thing that helped a little bit was a run around the park after tea at about 5.30. Someone on here once said I needed to exercise her like a labrador which I did .
I do honestly think that some children just need less sleep. I also think the toddler years when they have so much energy but not enough ability to get rid of it all throughout the day combined with an inability to listen to reason is the absolute pits (if that all makes sense).
Anyway, sorry for the essay. To answer your original question, when DD was getting up really early I used to snuggle on the sofa and doze whilst she watched TV/DVD. It feels like your life is passing your by - especially in the winter. Its AWFUL and I really feel for you. I used to think I should do some yoga or make food for the freezer but at that time you just have no inclination at all.
I hope your wake to sleep works - I was never brave enough to try it.