I don't think that the Exo-Terra will hold a full 8 inches of water. That being said, I think a Green tree frog is probably a good choice for a paludarium inhabitant, based on my own experience.

I had a pet Green tree frog in ancient times (about 30 years ago) that I kept in a 20 gallon tank. The setup was essentially all water, probably about 6 inches deep. For "land" I had a good sized Dieffenbachia with the pot placed in a ceramic holder in the water, a small slate platform, and a couple of good sized climbing branches. The frog shared the tank with a couple of newts and (temporarily) a couple of bullfrog tadpoles/baby bullfrogs.

Now, I really didn't know what I was doing as far as frog keeping at the time, but the frog lived in that setup for several years, and seemed happy.

I think that a Green tree frog would be unlikely to drown in such a setup, as long as there's plenty of climbing areas, as they naturally tend to live in swamps or marshes. Tree frogs that rarely have contact with water are far more likely to drown in such a setup.

I don't think there would be any problem with keeping shrimp with the frogs. Mine never seemed bothered by either the newts or the bullfrogs.

I don't recall there being any problems with the crickets. I'm thinking maybe the newts got the ones that fell into the water. I don't know if the shrimps would do the same in your setup?

ETA: Just took a look at the driftwood your thinking about. I would probably go with something thicker and more robust, more along the lines of the ghostwood pieces at the same site. http://www.bloomsandbranches.com/SearchResults.asp?Cat=1845 ( no grape wood, as that doesn't tolerate humid conditions).