A misachek b’kubya (lit. a dice player, the gemara’s term for a gambler) is pasul eidus for two reasons: a) it’s k’ilu gezel (because the other players hope to beat him, so they don’t have real yei’ush on their money) and b) he is not involved in yishuv ha’olam. The second reason would not apply to an occasional gambler.
I have not heard anything about gambling with respect to the Satan, or that it extends to the gambler’s family.
(This is me, not my husband; I just learned it last week).