You have a boat and enjoy it. Will you be able to tow the boat and a trailer at the same time? Or will you have to leave the boat at home so you can use the trailer.
With only 2 or 3 trips a year, and you already have a nice outdoor property, I'd go with the tent. Your kids can use it at home during the summer; you can have 2-3 four to seven day trips with it in the summer while still being able to tow your boat. If you find you use it more than you originally thought, then you can easily move up to a trailer - most of the other camping gear you buy will move up with you to the trailer.
