I don't think that you should necessarily rule out using the resorts. They are pretty cheap at that time of the year and the kids will probably make use of the air-con at night, even if you can put up with the heat. There are some cheaper ones on the Tonsai side of the bay (in fact Tonsai Bay resort is probably what you are looking for). The bars on the beach are great for meeting other climbers and Momma's Chicken is a good place too. However last time I was in Tonsai there rumours of the MBK company building a resort smack bang on top of where Tonsai is. It seems like it is something that is always going to be happening "next week" though. I guess you will know if it is happening when you see the first bull dozer.
If you are climbing with your kids I recommend staying on the Railay side so they can top rope the easy routes on the beach (the one with the cave full of c--ks, I forget the name). At the other end of the beach is Escher World Wall which has a couple of easy routes and some harder stuff for yourselves. By staying in Railay you will avoid having to get your kids over the slippery jungle paths that connect the two villages. These are easy to negotiate with just your gear, bat are a pain with baggage and I guess kids would be even worse.
Guides are pretty easy to find from basecamp and Wee's (?) climbing shop, however in all honesty you are better off buying the climbing book and having a chat to everyone else climbing there. Idk what nannying services there are but being Thailand I'm sure there will be something to fill your needs. Make sure you pack deet and a solid amount of dressings for mosquito bites and cuts as wounds that get water in them don't heal too rapidly. I also wouldn't recommend swimming in the bay off Tonsai as all the sewerage ends up in there. Maybe buy some cheap sandals to access the climbs from; I tend to make the mistake of just wearing thongs that slip and slide from rock to mud to rock on the jungle routes. Runners just get wet in the surf and muddy and are less of a pleasure to use in my opinion.
Most of all have fun and make sure you do some of the multi pitches.