Great movie, I must add, seen it a few times and it never ceases to really get me thinking. As for the characters, this is what I'm speculating..
The father- ExTJ
The mother- ISFJ, maybe ISFP.
The grandfather- INTJ
Frank (Steve Carell)- INTP
Dwayne- INFP (slightly deranged)
Anyways, just trying to get an overall veiw, thanks!