Barry, I agree with Kirby.
635 South (or West, whichever it is at that point) to I-30 West to the Hwy. 360/Six Flags exit. That exit is a big loop. You'll go under Hwy. 360, and straight ahead is the entrance to Six Flags. It's about a 30 - 35 mile drive, and will take almost 1 hour. The worst part is right in downtown Dallas...make sure to follow any signs that say Ft. Worth or 30 West (at one point, there is a 3 way split in the freeway).
I would leave between 8 - 8:30 to help insure getting there before 9:30 for the Friday meet. You'll be coming from Houston for the Thursday meet, right?
I'm expecting the parks to pretty crowded this week, because of the local Spring Breaks (Dallas, Ft. Worth and Arlington are all out this week).
Parking will probably be $9 for regular parking, $12 for VIP. At least that's what they charged last year. Usually, there is parking at a little strip shopping center right before you enter Six Flags property that is cheaper and the walk really isn't bad if you want to save a few bucks.
When leaving Six Flags to go to the hotel, Turn left out of the Six Flags parking lot and follow the signs to I-30 (you'll go by the Judge Roy Scream coaster (wooden out & back, painted white). Be very careful as you go under Hwy 360, the signs and lanes can be confusing. Follow the signs to I-30 East (Dallas). You'll be on 30 for about 25 or so miles. Take 635 North (or East, whichever it is at that point). 635 to Northwest Hwy, Right on Northwest Hwy and Right on Pendleton.