Chesapeake Beach and North Beach are a great area. Nice schools, beach access and boardwalks in both. We've lived here (Chesapeake Beach) for 4 years and have really liked it. It's very family friendly.
It's a short drive to Prince Frederick with a large hospital and plenty of shopping. Although, the local market is fairly decent for a small place, decent selection and prices.
It's also not too far from Annapolis and DC, so commuting for work or additional shopping options isn't that bad at all.
Shadyside, Deale and Rosehaven are pretty nice too. We looked in these areas before we bought in Chesapeake Beach. I especially loved Rosehaven as it was right next to the Herrington Harbor Marina which is a lovely place, but at that time everything there was priced out of our range, which was admittedly quite low.
There's a lot of small coastal communities all down the length of Calvert County between Chesapeake Beach and St. Mary's-- Breezy Point, Plum Point, Dares Beach, etc you may want to look into as well.