Took my pirate-obsessed son, with family and friends, on the Family Fun cruise for his 7th birthday in October 2016. It just so happens that we scheduled for a wet, rainy Saturday. We were the last tour of the day, and I never saw any lag in enthusiasm from the crew. Everyone was excited and ready to have fun, despite the weather. My son definitely had a great time. I imagine that the views would be beautiful in nicer weather. My only critique is that I would like to have seen a broader variety of activities for the children on board. I remember there being face painting, some line dancing, limbo, learning pirate lingo, running back and forth across the boat to shoot the "cannons" and that's pretty much it.
I'll add that right before we boarded, I dropped my iPhone in the parking garage and shattered the screen. I told one of the crew members about it, and he was nice enough to have the bartender make me a free drink!
Over all, a good option for a fun family weekend in DC. Bring your ponchos if it rains.