I suggest 2 rooms at a moderate. Being your 1st time you will be spending most of the time in the parks, and while you will want some down time at the pool and such, moderate pools are great, with slides and cool theming.
If you stay at AOA - while it sleeps 6, who will sleep on the pull out couch? not very comfortable, and the pull down might not allow enough room for both kid's to sleep comfortably. Some friends did this at AOA and they gave the room to the grandparents, and they slept on the pull out she told me they were very uncomfortable, as her husband feet and lower legs hung off the bed, and the pull down was not big enough for 2 kids. 2 and 4 - she said they went to Wal-Mart and got a blow up bed and her husband and son slept on it.
With 2 rooms - 2 bath rooms, and 4 beds (queen size now in most mod's), and the kids could take turns sleeping in grandparents room, which is special treat for them. It also gives the adults some privacy while getting ready for the day. We did this when our kiddos where little and it worked out great, we had room with the adjoining door in between, which the kiddos thought was cool.
The pools are open year around at the resorts and heated, we have been swimming while visiting during Christmas,- October is another good month, You could do the Halloween party,
MNSSHP - It would be fun everyone can get dressed up, and trick or treat. Great Memories.
Not sure if you are doing the dining plan, you might want to check this out, There is a lot of chatter about the dinning plan, We love it, DH loves know that all the meals are paid for ( we do ddxdp which works for our family)I like knowing everyone can get what they want, You have to make that choice, but do check out this option. Character meals get very expense, but they are a must do at this age, most are buffets which everyone can find something, the characters come to you at the table, which keep you from having to stand in line to see them and get autographs, and air conditioning, and taking a breather from the parks.
YOu can check out menus and photo here and over on Allears site, This biggest tip I can give is make advance dinning reservations, ADR,
Check out park hours, parade time, Hard ticket events ( such as the Halloween party, Christmas party etc.,,)
Okay this is the biggest tip I can give, Know that your not going to be able to see it all, enjoying what you can see and do. Make the Memories..
Have a really magical time.