Any advice for hotels, things to do?
For hotels, if it were me, I'd probably make very loose plans and play it as it goes. I'd pick a target area for where I'd like to spend the night and find a place when I got there or when I'm ready to stop. I personally would probably camp for (at least) one night, probably at Acadia.
as for things to do at Lake george, it's been ages since I've been there and I don't really remember doing very much, but here's this from another thread:
Take out a boat
Six flags (if it's open)
Arcades
Mini golf
There's a sick tree climbing place 20 minutes north
There's a beach (never been)
Hiking
Rafting/tubing
indoor rock climbing
I believe there are also some museums
At Mt Washington you can drive or take a train (or hike if you're really feeling adventurous) to the summit. IIRC both are expensive. but beware, those are on opposite sides of the mountain so make sure you go to the right place.
At Acadia I would normally suggest the beehive trail, but I don't know if you want to do that with a baby... I think thunder hole is pretty cool (best seen at high tide...)