Loved the connecting rooms on the 7th floor in the premium rooms @ Hojo's, we were able to stay there in March 2010 and didn't find it noisy in the least. We live in a small city that we are not used to freeway noise and in those rooms we don't notice the noise. On the other side, the kids suite room side, we do notice the noise but it's not bad at all, and rather soothing. The beds are THE MOST comfortable I have ever slept on, so are the down comforters. Oh my gosh. I wish I lived there! We had a situation where 2 young boys would be staying (12 and 13 years) in that room, and we were told they couldn't guarantee adjoining rooms, more for the fact that something can happen the day before, such as water damage, broken plumbing, etc. that may not allow the rooms to be connecting, so yes, they were great about it, and did follow our requests through, but at the same time, they had to make sure that we understood that due to unforseen circumstances, should they arise, that they simply could not guarantee a connecting room... I think they will probably accommodate your needs easily, but, it might make more sense for you to grab a kids suite if you can. There is plenty of room there, rooms are nicely decorated, and 2 bathrooms as well, too.
The walk isn't bad at all, our DD did the walk easily when she was just 4 years old. You will walk around so much in the parks that the walk to and from Hojo's is non-negligible IMO. I did the walk 3 times one day, and it was manageable. Some days we did that walk twice. Having McD's close by is good for snacks on the way back from the park. Having Mimi's restaurant close by is a HUGE perk, as is the water park, the in-room safes, and the super staff.
Have a fun trip, OP!!

Edited to add; the way the doors connect, is that the room farther from the end, inside, between the 2 rooms, had a doorknob to open the door into the other room. The door could easily open up and then remain open, there was no automatic closure on the door. The room closest to the end of the hallway had no way to open the door to come into the first room unless the came out of the door leading into the hallway and knocked on the door to get back into the other room. A person could place a small rubber stopper in between the doors if they didn't want anyone from the other room to be locked out of first room. I think this is how it was... can someone please correct me if I am wrong?