We have used our boat in campgrounds frequently while trailering to cruising areas. You'll need a 30 amp adapter to go from the marine connection to a standard campground 30 amp. You can get that at West Marine or you can make your own with parts from any electrical supply house.
Having hauled our boat coast to coast quite a few times, we have run into an occasional rare campground/RV park that doesn't allow boats. Their loss, as there will always be another place down the road. Because our "water situation" is different from RVs, I think they have had experience where inconsiderate boaters have allowed gray water to run out... a very big no-no in most campgrounds (although some allow that). So, you can't use your shower or even your sink if they run out overboard when in a campground. We put a plastic wash tub in our sink and then dump that out in the sewer connection, discretely. Most of the time, we are welcomed in parks and campgrounds and have met some nice folks who are interested in our traveling style.
Although you didn't ask, there are ways to save $$ while land traveling. We belong to a variety of RV discount groups (having been RVing over 300,000 miles); the one we use most frequently when land traveling is Passport America, which saves you 50% at participating campgrounds. When all you need is a place to park for the night, and want electricity and a shower house, these can be an inexpensive way to go, if there are member PA parks on your route. If you don't need the hookups, another inexpensive alternative is:
http://www.freecampgrounds.com/ Many of those are city parks that allow camping for $10 or less, or dry camping alternatives, like Wal-Mart.
While some on the C-Brats have referred to their boats as a "boaterhome", there are some aspects of the boat that can't easily be used on land and in campgrounds, like the gray water situation or air conditioning if you have a marine a/c. But, it is the bed you are used to, you don't have to pack/unpack, you can use your microwave and other onboard amenities, many parks have cable TV and nice amenities like swimming pools and hot tubs. Just one of the real advantages of a trailerable boat.
Best wishes,
Jim B.