Marina district gets my vote..Harrah's is fine and the Borgata and GN next door are nice places as well.The clientele is better as you need a car to get to the marina district..the boardwalk? A bicycle..more people there asking you for a dollar etc.
Borgata has the only remaining racebook in town also if that interests you.

I'd check ahead to see who is appearing at the Pool that weekend you go,some crowds get a bit rough and that spills over into the casino..not the case when I saw David Hasselhoffs crowd there but much different with some dj's or Snookie types..Packs of kids drinking and occupying the walkways,not suitable for your children to be around.

I'd also check if the pool is 18+ in the daytime,I'm not sure but alchohol is served there..