I guess I'm just going to reinforce what some others have already said. South of Dallas along 287 starting from Midlothian through Waxahachie and on to Ennis will all be better than 4 minutes of totality. My backyard in Waxahachie will be 4 min 20 s. The center line passes over Lake Bardwell and just to the south of Ennis proper if I recall. The center line yields an additional 5s of totality but hardly worth the extra driving. Your biggest problem will be driving on the day of the eclipse. I was in middle of nowhere Wyoming for the 2017 eclipse and we still got them the afternoon before the eclipse (and had a bit of trouble finding a spot to park but did succeed towards dinner time.
DFW will be FAR worse because of the population density. I'm recommending to my family coming up from Houston that they come up Saturday morning for the eclipse on Monday and I'm a bit concerned that might still be bad traffic. This won't be hurricane Harvey when people were stranded on I45 for 23 hours but it's going to be closer to that than to normal traffic for sure.
The state parks are out unless you already have reservations. In all honesty your best bet is going to be some parking lot in some Walmart somewhere along the line of totality. There are large fields adjacent to both colleges in Waxahachie as well as at the Civic Center and as of now I've not heard about any formal events in town for the eclipse. The college kept talking about it but both myself and the Planetarium Director retired last year (partly in my case to make sure I wasn't going to be pulled away to do some public outreach crap during the eclipse) so that killed their plans as far as I've heard.
If we have rain before the eclipse day fields will be a NON-STARTER because of the high clay content of the soils around Waxahachie. Did you see the news reports during Burning Man??? Not quite that bad but sinking up to your axles is not unheard of. If there's rain within a day or two of the eclipse then stay on paved parking.
Pretty pessimistic from me I know but you need to have realistic expectations so you can plan accordingly.