This kind of rental doesn't seem possible. Sleeps six (though three should be kids--the space in the loft is tight, as is the top bunk) very comfortably, and is literally feet from Campground Beach. There are plenty of spaces to spread out--upstairs on the deck looking at the Bay, on the porch around the grill, or in the spacious living room. There is a lot of house crammed into this cottage.
Nothing is assured, but sometimes you get lucky and a cottage has a boogie board or something you don't want to have to buy or cart around. This place has the jackpot: for our stay. We had three body boards, two beach umbrellas, three skim boards, floaties, a surfcaster, clam rake + bucket (we didn't get licenses, but the option was nice!), kites, a metal detector (!), tons of beach chairs. Lobster tools too, for those so inclined! Don't forget some games, puzzles, WiFi, and an elaborate AV setup to keep the kids entertained.
It would insulting to list any faults I have with the property, as they really do pale in comparison to all the superlatives. They are easily overcome/ignored, and I would recommend this place to anyone--especially families with younger kids.
If you are going to be staying Cape Cod Bay-side, I cannot stress enough how much it's worth to be in comfortable walking distance to a beach. Save your parking money for an Ocean-side jaunt or two, and walk your family to an Eastham beach and experience the tidal flats and high tide swimming at your leisure. We went over to the beach up to four times a day. Try to do that loading up the car every time with young kids! With two parking spots and all the room, you will be the base of operations for relatives/friends staying elsewhere on the Cape.
Great place in a great location.