Just a FYI, At those parks on Lavon where camping is allowed,and I suspect other COE lakes too, unless you pay for a campsite, you fall under the day use rules. Parks open at sunup and close at sundown (not dark)for day use! You will be asked to leave on or before sundown unless you have a campsite. And, another FYI, some park attendants use a different time zone for sundown!
This is a good rule IMHO because as a camper, I don't want open traffic all night into the park. Makes it just too easy to git stuff stolen.