Building a 70 gal vivarium

I think you'll find that most of us will tell you not to mix species like this, particularly animals that don't occur together.

I will second John's statement.

Most if not all herpetologist will advise not to mix species as it will most likely cause stress to you animals due to many factors including but not limiting to : temp, humidity, size .......... and so on.
But if you do wish not to heed the warning as many keepers do not when they have a huge Viv....or tanks is my experience as a marine reef advisor .... keep to room-mates from the same habitat so require the same temp and humidity, get room-mates that are around the same size and will grow to the same size in adulthood and as your treefrogs are arboreal maybe terrestrial frogs would be a safer option.
My advice would be....get a few more green tree frogs of the same size and try breed them