The 7-day combination tickets (Historical Triangle Ticket, Spring Bounce Ticket) don't save you any money unless you spend multiple days at more than one attraction. Groupon periodically posts discount tickets to Busch Gardens. None of the other attractions offer discounts or promo codes.
Most things in Colonial Williamsburg can be enjoyed without a ticket. Don't buy tickets, especially if you have children over 12, too old to take advantage of the discounted price and too old to enjoy some of the cool activities aimed at kids, and spend your money on one of the evening ghost tours instead. Colonial Ghosts was well done, but next time we might try one of the costumed tours. Do buy the art museum admission for any art lovers in your group - it's huge, full of unlikely treasures, and open till 7. The rest of the group could fill their evening with shopping. The shops on Merchant Square don't offer anything particularly unique and the prices are outrageous, so check out the souvenir shops on Richmond Rd instead, and be sure to print out some coupons before you go.
Historic Jamestowne and the Jamestown settlement are two separate attractions operated by different organizations, connected by a nice bike path. Pick a sunny day and bring a picnic lunch, but don't forget to visit the indoor attractions as well: the Pocahontas movie in the Settlement, and the archaeology museum in Historic Jamestowne.
The Yorktown Victory Center has some interesting outdoor demonstrations, but overall it's not worth the price, at least not until 2016 when more indoor galleries will be added. It's a short free trolley ride or a nice half mile walk along the beach from the center of town. The Yorktown Battlefield has a little visitor center which is included in your Historic Jamestowne admission price, but the main attraction is a free self-guided driving/biking tour. It has a number of sites related to the 1781 Siege of Yorktown as well as a Civil War cemetery.
The Yorktown Bed and Breakfast that welcomed us, the Marl Inn, is changing ownership at the end of July 2015, but the new owners have promised to honor all reservations made before that date. The family suite includes two bedrooms (large and small), a living room with a couch and dining table, two bathrooms, and a fully equipped kitchen, all for $139 a night. It's a block's easy walk from the beach and half a block from the historic Main St. You can't go inside most of the houses, but there are a lot of plaques to read. Awesome.
In summary, I'd like to come back in the fall, with a larger group and bicycles. Save time and money by cooking most of our food and packing lunches. A 4-5 day itinerary could be designed to accommodate serious bikers as well as juvenile or recreational bikers, amusement park aficionados and history buffs, beach bums and art lovers.
P.S. Dan has this to say about Busch Gardens:
You can drop off and pick up your friends without paying for parking at a bus stop at the corner of Route 60 and Busch Gardens Blvd.
Bring your own food! While the food at the park is decent, it is WAY BEYOND expensive. Pack something that will not get ruined if it sits around a hot locker until lunch time. Or, if you drive in and have access to your car, put it all in a cooler with ice. And then just bite the bullet and purchase drinks for lunch or dinner. I didn't see any water fountains in Busch Gardens at all.
The park is not the easiest to get around, so plan your rides and how you'll navigate, and make plans to meet at a specific time and place for lunch/dinner rather than just relying on cell phones.
Take a break in the middle of the day to see one of the shows. It's indoors, air conditioned, included in the price of your ticket, and gives a nice break from walking around, which means you'll be able to stay longer and get your money's worth.