For KD, every other weekday is packed. It's weird. Dominator will be the most crowded from 10:00-1:00, because everyone is packing into the park, and that's the first thing they see. Oh, and even if KD says it opens at 10:30, you can ride some stuff at 10:00! The crowds will probably be on and off on friday, though.
Ok, just for if you've never been to either:
BGE: Ride Nessie. Just try it. Ride between the middle and the front so it's not too rough. RIDE GRIFFON, ALPENGEIST, AND APOLLO'S CHARIOT ALL IN THE VERY FRONT AND VERY BACK. That's extremely important. And Curse of Pompeii is pretty awesome, too. Not only a splashdown ride, but also a cool effects one.
KD: Ride Dominator if you get there before 10:30. From there, ride Berserker if you wish, and then head out to the back section. Ride Volcano (Sometime during the day, YOU HAVE TO RIDE THIS IN THE FRONT. SECOND ROW DOESN'T DO IT FOR HOW AWESOME IT IS) and then the Crypt, Anaconda, Backlot Stunt Coaster, etc. You need to ride Flight of Fear, but it doesn't open until 10:00 for some reason. It's really cool! If you've ever been to SFA, just think of Joker's Jinx, but indoors! And the launch is intense. Oh, and Schooby Doo's ghoster coaster is a fun ride to cool off on and if you've ridden everything else. And ride Drop tower XD! I almost wimped out, but that doesn't mean you should!
Ok, I think that's it. Have fun!
My suggestion for KD is head straight for Volcano. The line fills up fast and only gets longer. Domiantor's line is quick, unless you wait for the front row. Backlot Stunt Coaster and Richotet are quick and effiecient rides. flight of Fear can be bad, but the queue theming is the best in the park.
At Busch Gardens, start at Apollo's Chariot, then Curse of Dar Kastle and BBW, next Aplengeist and Griffon and finish off with Loch Ness.
Hope this help! Busch Gardens is all about the experience with great coasters thrown in and KD is mostly about coasters. Both are fun parks and giving yourself 2 days at each should help too.
They are a bit dated but should help.
And for KD, take a look at this post:
Also, here are the links to the BGE and KD park pages on TPI which contain ratings, reviews, and strategies for touring the parks:
Let us know what other questions you have, and remember to post your trip reports after your visits!
Walt Disney World
Tokyo Disney Resort
Theme Park Insider Books