I think you're thinking of the "villains unleashed" events, those were crazy, and probably won't ever happen again.
Club villain is very organized and limited in the amount of people. I haven't been so i can't comment on how it would deal with a 4 year old but ive heard of many stories/pictures of smaller kids there and enjoying themselves.
There's more variety of villains at MNSSHP, due to seeing them in the parade & stage show, but the m&g's with them are VERY limited, if you want to spend time actually talking with villains, then do club villain, if you just want to be able to see them, then it's your call.