Post Oak? Are you speaking of North Sentinel, just west of Twin Bridges, or the Dam location on the south side of the lake, west of the Dam? Both of those are closed in the "off-season" due to low admission rates. It sucks because both of those offer access to some of the better fishing locations. Bank fishing is entirely doable at Thunderbird. Like Dennis said, don't just sit in one spot. Take a limited amount of tackle and fish while hiking the bank. Have each child rig a different color/style jig and cast with a bobber set at between 12-18 inches, reel in the line 6 inches, let it sit, retrieve another 6 inches. This should get the crappie to bite pretty quickly, if they're in the area. Also, the docks are not for fishing, and the Rangers will remind you of such (I think it's ridiculous personally). There is a pretty nice fishing only dock off Turkey point on the south side of the lake that y'all might do some good at. It gets packed though, so either go early, or prepare to wear shoes you don't care about and hike around that cove with the above mentioned method. Good luck.
