If they put Han in, he wouldn't be a toddler.
If you think about it, they are most likely going to have Ep. III when Luke and Leia are at least 3 years old, as there is very little chance they'd remember their mother at any younger age (seeing how, in ROTJ, they talk about their memories [no matter how vague], I think they'd be good enough to show us how those memories were formed). Going on that, I'd put Han at about 8 years older than Luke (sure its debatable, but give the scenes and such of ANH, I think I'd be about right). So, if my calculations are correct, Han Solo in Episode III will be: 11 years old.
So just think of Anakin from Ep. I...only its Han Solo.
-Matt