If you want to hike Mt Washington I would stay at Dolly Copp CG(NFS CG) it is close to the MTN and visitor center for day hiking Mt Washington. For swimming or rafting there is the Saco river along rt 302 and Swift river along rt 112. Both have NFS cg's. What size is your MH? Mt Chocora is also a nice hike and less strenuous than Mt Washington. Blackberry crossing CG is close to that. If you like Mtn biking there are some nice trails off of Bear notch road through the Experimental Forrest. Jigger Johnson or Passaconway are nice CG's for that along rt 112. How long do you plan to stay in that area? How old are the kids? There are a number of kid attractions in that area also if your kids are young.