I have a cottage in Eastham and do not board on the Cape because of the restrictions in place during the summer. You can't kite on any of the
national seashore beaches. Truro is pretty rural with many private beaches that I'm likely not familiar with though the one on the ocean side of
Pamet River Road is incredibly beautiful.
IMO you would need balloon tires to buggy on the Cape. The beaches on the ocean side are narrow and often with bluffs or dunes that would obstruct
any offshore wind and foul a kite on any onshore wind unless the tide were out a good bit.
The sands on the bay side are really soft and often wet which means you will either get wet or need a lot of power to pull through the tidal eddies
and pools.
IMO, the best beach is Skaket in Orleans or Mayflower in Dennis. Both are likely to be good and crowded when you arrive with your gear. Skaket has
lifeguards which will likely not allow you. Not sure about Mayflower. There are great fields in Sandwich at the high school but that's a long
commute.
Race Point is wide enough but its part of the national seashore so no go.
The cape is pretty narrow out by Truro so I can't think of any open fields but I spend most of my time in Orleans and Eastham and Welfleet.
I'd just say prepare to be disappointed or take late or early day runs when the tides are suitable and the crowds are not.
Depower Quiver: 14m Gin Eskimo, 10m Gin Eskimo III, 6m Gin Yeti, 4.5m Gin Yeti (custom bridle and mixer)
Fixed Bridle Quiver: MAC Bego 400, JOJO ET Instinct 2.5 & 5.5, Lil Devil 1.5, Sting 1.2
Rides: Ground Industries