I think I would go with the plan to put them into the larger tank.
Get the plants up real high---they'll get there!

I converted a 40 gallon once. I siliconed a cheap black/plastic pictures frame onto the interior ceiling of the tank. The cross bars in the frame created a spot to help drape log pothos vines. I believe there is a photo of it in a smaller 10 gallon vertical in this thread:
http://www.frogforum.net/tree-frogs/...-supplies.html

You could try to feed less ..............daily? Try the bowl method of feeding if not already doing it.
Maybe, even use 2 bowls? Less food competition.
The bowl also helps to keep the dusted supplements on the crickets.
Develop a consistent dusting schedule ........assuring all will get what they need over time.

Just a thought

Funny........They really develop habits. I feed with clear glass bowls.....once I moved the bowl in one enclosure... I found all 4 the frogs- that night- sitting in the spot where the bowl was. Seeing something like this reminds me never to take for granted how stressed they get when they are moved, transported etc. They don't even like their 'stuff' messed with.

Have fun. Nothing like creating a new enclosure ! Post some pics as you go along ?