No you don't need reservations and yes you can use gas or charcoal
If you plan it accordingly and have at least ONE person get their (maybe an hour or so) prior, you should be good. Taking that hour to set up if you're going to do food and whatnot is perfect. I'm not sure if they still provide grills if needed, so if you're doing a BBQ I would double check, in case you need to bring one. I notice the Gazebo furthest to the right (the one that is closer to the water technically) is your best bet at grabbing it, as people try to unload at the closest one to the parking lot. If it's a family function I would suggest bringing a broom and running thru 1st, as just things from the trees, random trash, ect tends to gather.
Just make sure someone in your party gets there early if you want a covered picnic area.
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