Just past the entrance booth, there is a potable water connection that's easily accessible, if you should need to refill your tank. There is also a dump station there. It's located on the right side as you're going into the loop area and the turn off for E loop.
A shower, if done judiciously, can be over in 5-7 minutes with minimal water. Depends on how many people will be showering in the course of any given day. AND...there are solar shower bays in A loop, you have to bring your own solar bags and water, but it's available and doable.
If you're like most folks that are staying in Moraine Park, you'll likely not spend a whole lot of time in camp. Turn off everything that you can when you're not there. You'll not need A/C there, it may get into the upper 70s or so during the day, but cools down significantly in the evening and after dark. You'll be putting on the fleece and hoodies!