Just pack everything you could possibly need. Pack at least 2 outfits per day, at least 10 diapers per day, more food and drinks then normal since extra energy will be used. Pack infant tylenol and children's benadryl. Call your pediatrician to find out what kind of dose to give in an emergency. Bring the neo-to-go spray for cuts, bring a ton of baby wipes to use for cleaning.
Plan for all weather. I'd bring all pants and closed-toe shoes so you don't have to worry about poison ivy and stuff.. If you plan to swim, buy a life jacket for your son. Lots of bug spray, sun screen, etc. Read the labels and buy the kind meant for babies.
