AAA is a great source for maps, brochures, etc..
I would have to go along with Neil--stick with the ship excursions: especially with children in Mexico.
You don't really have to take excursions unless there is some activity you feel you "must do". You can safely walk the town and use the beaches in Puerto Vallarta, Zihuatanejo and Cabo San Lucas. The main part of P.V. is a short cab ride from the pier. In Cabo and Z. they are within easy waliing distance (well, maybe a real short cab ride in Cabo).
Not so in Acapulco; just a short distance from the glitzy hotels and clubs is grinding abject poverty. Stick with the ship tours; stick real close.