Aquariums do not mix with terrariums. Small ponds are all right, but if the frog falls into the water, it will be dead and soil the water and kill what else is in there.
Don't know much about tree frogs, so I'm not going to comment on that.
As for the glass, just buy a standard aquarium and use that. It will be thick enough for most things.
Also, I have a 44 gallon pentagonal aquarium with stand if you are in the Cupertino/ San Jose area in CA.