Just really a +1 to what the others are saying.....but if you'd like to do a Sorority/community, definitely don't go with the Angel. Its always important to remember that while he will be small when you get him, he will grow and he will grow rather quickly and become aggressive.
Besides the Angel, your plans look good. Just be sure to provide LOTS of surface cover with floating plants as your girls will be spending most/all of their time in the top level in that tank size. No tank is 'too big' for bettas so long as you can provide to proper amount of cover for them to be comfortable and, in the case of a Sorority, help break up the line of site to lower aggression.
A mid-level school(6+ that is)like the others are suggesting would be something nice as well. Rasboras are a personal favorite of mine....very peaceful, neat little fish....but most kinds of tetras would work just