Hoola Hoop Hoopla - make sure everyone has plenty of room if you have several hoops going at once. Create different challenges using hoola hoops - obstacle course, spinning challenge, bean bag toss, etc.
Beach Blanket Bingo - Everyone has their own beach blanket, homemade bingo cards with beaching items, use fish crackers for markers (and a little snack).
Water Play - This is great fun but you'll want to spread a tarp out. We used individual dish pans for each child with pouring toys. We also filled the small swimming pool with warm water so each child could enjoy a mid winter splash party. Warning - fun but wet!
Sand Play - Much like above; we'd have pans of sand or a sand in the swimming pool. This takes some planning but is so fun. If you have an area to keep a sand and water play set up throughout the winter it's even better. We used the basement and of course put a large tarp on the floor. Spills needed everybody to help to clean up.
Ball Pool Play - Alternative to water or sand play is to fill the kiddie pool with plastic balls for fun without all the mess.
Beach Ball Bounce - using small or large beach balls, configure a ball bounce obstacle course.
Summer treats like ice cream or even better icy pops are a special treat.
Fruit kabobs are a healthy summer snack.
Be creative! Ask the children what their favorite summer foods are and then make a menu plan.
Sun Visors - Decorate foam visors with foam stickers or jewels. All the materials are available from your local craft store or online suppliers.
Create Personal T-shirts - You can do tie dying or permanent marker methods for making your own beach day T-shirts.
Sand Painting - You can use colored sand or plan sand on colored paper. Remember it's the process not the product.