Hi MillyMolly, welcome to BlackpoolWeb.
The pleasure beach is in the south, as is south pier, and the waterpark. The Tower is between Central Pier and North Pier.
The North is fairly quiet not much there. Central Blackpool may not be best for families, its where most of the busy pubs and night clubs are.
As for evenings with families, in the South you have the Laughing Donkey Bar on the South Pier, they have kids entertainers during the summer. You have also got Tommy Ducks which allow kids till 9pm, they also do good food cheap, like 2 adult meals for £6.95 cant remember how much kids are.
The area between Central Pier and North pier may still be a bit of a building site as that's the last of the prom to be finished.
Evening entertainment sort of depends on the age of the kids. A great show is
Legends on Central Pier, it is a tribute act show and they have a bar. They have acts like Freddy Mercury, Robbie Williams, Kylie, Elvis, Elton John, Rod Stewart, Diana Ross. The line up changes and hasn't been announced for 2011 yet. They also have a compare that is kid friendly and funny

Check out
What's on in Blackpool or
Shows in Blackpool for details.
As for holiday flats try
Cleveland Court Holiday Apartments
Hope you have a great time.