Don't do the ADFs. The betta will most likely steal all of its food because ADFs are slow at grabbing their food where as a betta can snap it right up. These aren't appropriate tanks makes despite the usual recommendation. The frogs will end up starving. ADFs should only be kept in species only tanks IMO.
That's what I think.
Also, when getting Endler's, make sure your only get males because they will explode with babies if you get mixed genders. I don't believe bettas are good tank makes with Endler's because Endler's are so brightly colored, the betta may attack it, thinking its another male.
Flame - Red and Blue Veiltail Male
Oswald - Blue Halfmoon Male