Not sure if it is too late to answer your question but since I happend to know a bit about this park, I'd give a try for some tips. Yes, there are tents and various type of RVs for rent. I checked out some websites which could be useful for booking RV/travel package etc.. Unfortunately there isn't a site in English for me. Official travel site for Chongming is searchable at cmtravel-com-cn, all in Chinese. It shows contact detail (telephone 021-59338028) on the page, but I suspect if any advisor would speak/explain you in English - considering Chongming is a relatively undeveloped countryside of Shanghai. Travel agency such as Ctrip in shanghai could be better in this case. Public transportation in Chongming island isn't that ideal and efficient for the moment. So alternatively you could either call taxi after you arrive at a station, or drive on your own. Be ready to bring yourself enough to drink and eat, otherwise it might be difficult to arrange inside as the opening hours of restaurant are not regularly long. Be also aware the wild mosquitos if you stay overnight, they could be really tough ;-) Make sure you close the tent or RV door all the time, and don't forget to grab your shoes inside because it could be fairly humid outside. Good luck with your booking and enjoy your next trip. With best regards.