The ADFs won't eat the guppies. Don't get a trio or they'll breed and you'll have a severely over-stocked tank. I would say get 3 males or just 2 females. Remember that males are smaller than females and females can store sperm for several months so adding females is risky because they may already be pregnant. 3 males and 2 adfs is slightly over-stocked but manageable with regular partial water changes and good filtration.