In my earlier life, my wife's family would spend time at the Black Horse Motor Court in Holderness. As I recall, they had a nice beach on Little Squam with dock space for boats. The only downside was that we had to cross Route 3 to get to the beach from the cottages. The location is a short ride to the Meredith side of Winnipesaukee.
The business was sold at some point but they are still doing business as The Cottage Place on Squam. The web site is
www.cottageplaceonsquam.com
It looks like they have all the same cottages and amenities. This might be what you are looking for.