I absolutely LOVE creating rooms for children. While kids are fun to plan with, babies are easier. They don't insist on hot pink or purple as the primary color. So soft greens, tans, creams and blush can be used without hurting a budding young interior decorator's feelings.
A beach house needs to be comfortable and easy care, impervious to sand and salt water, with soft and calm colors. The view outside needs to take precedence over the view inside. That means distressed wood, stone, weathered paint finishes, easy care slipcovers, painted fresh white woodwork, and the muted colors of sand, sea, driftwood, sea glass, and shells. Toss in the cry of gulls, sound of surf and ocean breeze and a porch or patio to take it all in - and you have HEAVEN.