I personally have 5 guppies living with a male betta. It seems like fin nipping is starting to happen, so I'm keeping an eye on things. I feed mine a combination of different flakes, Tetra flakes and Tetra crisps because I need to get rid of the latter and I'm not going to just throw it out either. I've just got them fairly well crushed. Makes it a bit more difficult to judge feeding time, but I watch them like hawks to make sure one's not getting too fat or too skinny.
Bloodworms should be given on a treat basis I've heard. They don't have hardly any nutrition so it'd be like candy or something for them. Egg yolk is recommended, I've heard of both liking it. *Nodnod.* Live foods can be small flies and various other things as well. They all need lots of protein.