Busch Gardens does offer a ticket that will get you 7 days of admission to Busch Gardens & Water Country or you can do one that includes Colonial Williamsburg. Kings Dominion is around an hour away from Williamsburg and they have a bunch of coaster along with the Intimidator 305 giga-coaster and they have a water park inside the park.
Oh, and if you want to compare the coasters:
-Grover's Alpine Express (Zamperla kiddie)
-Loch Ness Monster (Arrow Custom Looping)
-Alpengeist (B&M Invert)
-Apollo's Chariot (B&M Hyper)
-Griffon (B&M Floorless Diving Machine)
-Air Grover (Zamperla Kiddie)
-Cheetah Hunt (Intamin Launch)
-Sand Serpent (Maurer Sohne Wild Mouse)
-Scorpion (Scharwkorpf Loop Coaster)
-Kumba (Custom B&M Looping Coaster)
-Montu (B&M Invert)
-SheiKra (B&M Floorless Diving Machine)
-Gwazi (GCI Dueling Coaster)
-Shamu Express (Zamperla Kiddie)
-Journey To Atlantis (Mach Water Coaster)
-Kraken (B&M Floorless)
-Manta (B&M Flying Coaster)
EDIT: Also, for those of you who like something other than coasters, Busch Gardens Africa has many animal exibits along with a cool nighttime conert-like show as well as an enclosed theater, Cirque-du-Solei-like experience.
Sea World has aqll of its animal/sea life exibits and many amazing shows with Dolphins, Sea Lions, and of course Shamu, all leading up to a special nighttime water, light, and firework show spectacular!
SheikRa (FL) is comparable to Griffon (VA)
Montu (FL) is comparable to Alpengeist (VA)
However, Tampa does not have anything like Apollo's Chariot, which is one of my personal favorites, and a highly rated coaster on this site.
Since you're taking the water parks into consideration, though, I would probably go with the Florida duo.
I've also done the Busch Gardens- Kings Dominion tandem. . . some good coasters at Kings Dominion, like Volcano.
* The location of the park is beautiful (The Tampa park is located next to a bad neighborhood)
* It has a dark ride (The Tampa park has none)
* It has a great riverdance show (the Tampa shows are average at best)
* The park is nearby colonial Williamsburg which is so special! (the Tampa park is nearby a university--not very interesting)
On the other hand, Busch Gardens Tampa has animals (BGW does not have them) and with the new coaster (Cheetah Hunt)BGT will have the edge over BGW when it comes to coasters.
The only thing I would say BGT has going for it is above BGW is the animals. If that is something you are really looking for, by all means go to BGT as it is essentially a theme park with a zoo.
As far as the weather goes, I would actually say the temps are comparable. The benefit to Virginia is in June the humidity isn't as bad as the late summer, whereas in Florida the humidity sets in in early May.
And while BGW may not have as many coasters as BGT...BGW has some of the top ranked coasters in the world. Loch Ness Monster is the first and only coaster IN THE WORLD featuring interlocking loops. Apollo's Chariot is one the the top 10 steel coasters in the world. Alpengeist is the tallest and fastest of its kind. Griffon was the first FLOORLESS dive coaster (SheiKra was the first dive but had a floor, which was taken off after Griffon was built). Also by June the new Mach Tower drop tower should be open which takes riders 240 feet in the air displaying Williamsburg's amazingly beautiful views and will then drop you at 65 mph straight down. Also over in Water Country (the waterpark), the new Vanish Point will be open. This is the tallest slide in the park (75 ft.) and features 4 slides in the tower. 2 of which force you to literally push yourself over a very steep drop. On the other 2, you stand in a box and the floor suddenly drops out from under you and leaves you free falling.
While BGT has more rides and probably nicer weather, BGW has plenty of going on, is the world's most beautiful theme park, has incredibly nice employees, and is steps away from some of the most historic land in the country.
As you can tel...I'm BGW all the way =)
The Williamsburg park is gorgeous, in my opinion. That may be something of interest for some of your group members. It is very "green," and I really liked that. I went last June, and I remember it being pretty brutal, weather-wise, but I seem to recall hearing about them pushing near record highs (mid-90s, if I remember correctly), so my experience was probably unusual in that regard.
Festhaus=awesome. As an additional note on roller coasters. . . you could ride all of the rest of them at the Tampa location, or you could just ride Apollo's Chariot a bunch of times instead in Williamsburg. I would probably take Apollo's Chariot, though the other ones are fun, too.
I do have a question, though. . . does anyone else have trouble getting from Point A to Point B in the Williamsburg park? I remember thinking it was pretty large.