This is just my opinion, but I would be inclined to let him sleep as close to 8am as possible so he does get the 12 or so hrs that he needs for now. I guess there are a couple of factors: when will you be returning back to work and needing him to be up at 7am? Also, as he gets a little older and coping with longer awake times and not as prone to melting down at bedtime, he's less likely to need a lot of separate settling time from dd - he may end up being the first to bed and then dd or mabe you will be able to bring them closer. I've just oberved this with my two and dd goes straight to sleep now and my ds is now very easy to put down to bed so both are in bed at 7pm (it is tricky and fortunately DH is around most of the time so we have one each to sort out). But if I'm on my own they are both bathed at the same time, dd is breastfed while I read to ds and then I put dd to bed and then return to ds (on the odd occasion I've been going back and forwards between their rooms resettling).
So I guess it kind of depends how urgently you need to get this sorted for an earlier wake up. For now I'd just go with it until he's a little older and the situation will change naturally.
HTH
