If you give the ADFs hiding spaces (uprooted plants for them to hide under work great), they *should* be fine. However, everything depends on your individual betta, because while ADFs do hang out on the bottom of the aquarium, they like to float on the water. Food is another issue. They don't really like sinking food unless its live, so your betta and frog(s) will be competing for food. I had a male betta in a 2.5 minibow with two ADFs and they got along fine, but other people haven't had such luck. Unfortunately, what it comes down to is trial and error. You're never going to know how your betta reacts to a tankmate unless you put them together. And the best thing you can do is properly decorate the tank to give each creature their own space.
Alexa