Due to the size of your unit you will be restricted and must plan your turns ahead..
Many campgrounds like Somes View ( which is lovely) cannot take your unit. That said all the campgrounds that can handle that size are outside the NP.. Be aware that in 2020 there may be a reservation system so you must preplan your days too for your visit in the Park
The traffic is getting insane
Mt Desert Narrows is just on Island and has what you need. Does have a pool.. tts companion Narrows Too is just off island and is actually lovely with a pool.
Oceanside KOA is just on island and is right where rt 3 curves to the left. It is easy to miss the entrance.. There is a second one down the road but the sharp turn has put at least one fifth wheel in the ditch( we saw it). If you choose that one and miss the turn go another mile or two down 102 to Town Hill where there is room to make a U turn.
Oceanside does not have a pool.. Pools are rare where the temperature hardly ever gets above 80
Bar Harbor Campground is just outside of BH.. It has a heated pool. But does not take reservations or credit cards. ( this is strange to me but I have been by there and it seems fine!)
We live about two hours away and will head to Acadia in a week or so for the Night Sky Festival.. We never go in the summer!