One way to bring back memories of a summer at the beach is through beach themed decorating. It is also a way for kids to have activities in crafts and maybe even make a special gift.

I like to start with the bathroom (for me the most obvious room to start with); there you can add pictures, either sketches or framed photographs to the walls. I think enlarging your own picture (especially if it includes the family) looks best.
Towels with starfish, seahorses, seashells, of fish look great. Again, as with the picture, I think it can be more enjoyable for the family if you start with plain towels and wash clothes, then sew on or embroider your own beach or ocean themed designs.
Soaps can also have a beach theme. Place your soaps in a shell container, or even make decorative soap by carving your own designs in them (Ivory soap works great for this).
A fishing net embedded with starfish (or even a puffer fish) hung near the tops of the walls really brings home the beach theme for me. Then there are decorative shell baskets (which are easy to find on-line). These Shell Baskets can be placed on shelves or just the toilet reservoir. A final touch to the walls would be a shell night light to add evening illumination to the bathroom.
One more suggestion if one is feeling industrious is the flooring. You can find linoleum tiles that have fish, shells, or anything beach related and place these on the floor to finalize your bathroom.

As for the kids; the Shell Baskets I mentioned earlier are an inexpensive way to get the kids involved. These baskets usually come with many different seashells that can be used to make all sorts of design, murals or beach diorama.
The diorama is my favorite for kids. Use the shells, some fine sand, maybe some starfish (there are inexpensive dried starfish available on the internet), and even some plastic fish. Use blue plastic film to represent the ocean, cotton balls for clouds, maybe a toy boat too. The little drink umbrellas are great to use as beach umbrellas. You can glue broken shells together to form a reef too. This project could also be used for the kids to make inexpensive Christmas gifts for family members that show a little more thought than the average gift. This a also good project for kids to bring in to "shut ins" that used to enjoy going to the beach.
Back to the Christmas idea, seashells can be turned into great Christmas ornaments too!

The garden is where my wife likes to add a little more ocean themed flair. She enjoys the Pangansin shell wind chime with the urchin spines that make musical notes. I personally more like the flowing beauty of a stairway (spiral) shell wind chime.
In the garden next to a hammock or just lawn chairs is a good place to hang the shell wind chimes. You can even construct a more life-like "out door diorama" using a small pond with a fountain head, beach sand or whatever similar is available, again some starfish and seashells and you have your own personal beach space. This can be a little more difficult in colder climates, but the pond can be turned off in the winter, and/or covered with a tarp to prevent damage from falling leaves or whatever else fall and winter bring.