Well, I've been wandering through the letters. The best I've been able to accomplish is a set of three 8-letter words, none of which would be used to describe most mothers. Anyone been able to do better with a 9-letter word perhaps? If not, I'll give you my three 8-letter words after the deadline.
Draw a five-by-three square rectangle, five squares wide by three squares high. Fill it with the letters from Happy Mother's Day, in order:
The object is to spell the longest common English word in the grid, following the rules of Boggle. That is, proceed from letter to letter, following connected squares horizontally, vertically and diagonally. Repeating a square is not allowed.
Edit: Okay, time is up. Since I first posted, I've found one more potential answer, so I have four 8-letter words.
The words I found were:
HOTHEADS - Quick-tempered or impetuous persons.
POTHEADS - Slang term for habitual smokers of marijuana, see Stoners.
HOPHEADS - Slang term for drug addicts.
MATADORS - Bullfighters who perform the final passes and kill the bulls.
The first 3 aren't very flattering for a Mother's Day puzzle, so I sent in my official answer as 'MATADORS'.