Glad you're going to stay at least some days on-site!
I don't know which on-site hotel's the best, but the DIS podcast did choose the DLH! For your first on-site stay I don't imagine you can go wrong staying there. Then again, all the hotels are nice.
Some of the rooms at the GCH can be quite far from the hotel exit, so if you're unlucky you could end up with a surprisingly long walk. You can always request a closer room, and depending on how you look at 19 weeks, you might or might not score a bit of sympathy with the staff to help you get one.
The Paradise Pier elevators can be a pain, but I think you can have your DH squeeze in a down-bound elevator and then he can use the glass elevator to get up to your floor. Plus if you really don't get to the parks at park opening, they may not be as busy when you want to use them.
I don't know how easy it is to get a view room at the PPH without paying for it, so I don't think I'd count that as part of your decision. The non-park view rooms have (IMO) a worse view than many of the rooms at Hojo!
I'm 95% sure you can use the pool after you've checked in to a Disney hotel, even if your room isn't ready.
Have a great trip!