I don't know how old your DD's are, but if old enough then definitely rent bicycles for the length of stay. Makes it very easy to get to the beach and there are a lot of bike paths to enjoy HH.
Here's a list of other options copied from a travel site:
Bicycling
Revel in the romance and beauty of the area. Rent a bicycle and peddle the easy paths.
Disneys Kids Night Out Challenge
(Additional fees apply)
Fun and challenging activities for kids around the resort.
Disneys Kids Night Out Movies and Pizza Night
(Additional fees apply)
After a terrific pizza dinner and games, the group will head to a local movie theater to see a recent release.
Teens Night Out Movies and Pizza Night
(Additional fees apply)
Teens eat a terrific pizza dinner, play games and join the group to the local movie theater to see a recent release.
Un-Birthday Party
Celebrate the 364 days of the year that arent your birthday with party games and cupcakes.
Teen Activities
Teen Mini Golf
Teen Capture the Flag
Teen Billiards
ITeen Hoops
Longview Arts & Crafts
Release your creativity with these great activities that teach you to make:
Vacation Pillows
Memory Boards
Picture This!
Disney Character Mugs
Mickey Tie Dye (Additional fees apply)
Gyotaku Japanese Art of Fish Painting
Find out what the ancient Japanese art of fish rubbing is as you paint a T-shirt to keep.
Nature Photography
Learn how to improve your photography skills.
Sand Sculptures
Already mastered the sand castle? Come learn how to create sea-animal sand sculptures.
Beautiful Butterflies
Learn about butterflies and go on a walk to feed the resident winged beauties.
Getting to Know Birds
Get tips on using binoculars to identify the low country's rich avifauna. Learn basic birding techniques. Lists are complied on each walk and a complete record is kept of the birds spotted on the resort.
Meet the Naturalist
(Additional fees apply)
Join our naturalist in an informal chat to find out the answers to those burning questions about nature and anything else you'd like to learn a little more about!
Golf
Golf and Golf Lessons
(Additional fees apply)
Call the Concierge desk up to 60 days before arrival to book tee times at nearby golf courses.
Disney's Hilton Head Island Resort has discounted rates and packages set up with the following golf courses:
Hilton Head Plantation
Palmetto Dunes
Palmetto Hall
Port Royal Plantation
Shipyard Plantation
Indigo Run
Sea Pines Harbour Town Golf Links (Site of the Heritage Golf Classic)
Hilton Head National Golf Course (Off Island)
Island West (Off Island)
Eagle's Point Golf Course (Off Island)
Old Carolina Golf Club (Off Island)
Old South Golf Club (Off Island)
The Crescent (Off Island)
Excursions
Low Country Nature Dolphin Tours
(Additional fees apply)
Get to know dolphins on a first-name basis during a 2-hour tour on the open coastal waters.
Local Historical, Cultural and Nature Tours
(Additional fees may apply)
Tour Hilton Head or Pinckney Island, or walk on the beach with a knowledgeable naturalist.
Nature Kayaking Trip
(Additional fees apply)
Take a guided 2-hour adventure that features a pre-trip overview of Kayaking fundamentals. As you paddle, you'll hear fascinating island history and learn about the coastal marsh ecology. For even more adventure, ask about the Sunset Nature Kayaking Trip.
Shark Fishing Adventure
(Additional fees apply)
Join us aboard the Tru-Blu as we catch and release many different kinds of sharks, rays and trout.