I think I remember reading that curved beaked birds (like budgies and parrots) and flat beaked birds (like canaries and finches) shouldn't be housed together. Although, given enough space, I think canaries and budgies might be ok. Maybe just start out with a couple of each and have a back up plan in case they don't get along. For example, have someone that can take either the budgies or the canaries on standby.