Question:
Can an avel play dreidel during Chanukah for money?
Answer:
An avel shiva should not play dreidel, because he should not come frivolous behavior during the shiva) unless he is doing it in order to preserve a specific minhag). However an avel during shloshim and the rest of the year would be permitted to play dreidel during Chanukah, as it is not considered like being metayel.
Note; The poskim strongly discourage playing cards etc. for money. .
Sources:
Y:D 391-1,Aruch Hashulchan ibid 2, M:B 671 D:H Vnohagim, Aruch Hashulchan 670-9.
