I would defiantly say Seabrook, NH. It's the closest town to Boston in NH, right on the ocean, schools are good, lots of shopping and one of the lowest property taxes in southern NH. I personally live in Seabrook and know the area well. Other areas to consider a little farther north is Hampton Falls, Hampton and Rye, all on the ocean. Please contact me if you'd like to let me know what your looking for and I can help you find it!