I was there last week and didn't notice much for mosquitos, at least not in the D loop.
We were one of the lucky few to have a decent-sized tree in our site, but with some crafty angling of the motor home and toad, we were able to fit both with just enough room to get the awning up.
They give you a punch card with two showers per day. We just used our RV shower and kept the card as a souvenir.
The water is free, just note that you'll need to fire up your water heater ASAP. Unlike the rest of the park, the water coming out of the ground is COLD!
Regarding electrical service, we were seeing about 110-112 volts most of the time on 30A service, so be aware of that as you use your more sensitive appliances.
If you plan to use the laundry facility there, go before 4pm to avoid waiting in line for a machine. There were a few that were out of order when we were there.