We moved here from NC about 20 yrs ago and we miss the convenience of hopping to the beach in 3 hrs.
Great thing about Dallas is that the airport is fantastic and you can get away to either coast fairly quickly.
We go to South Beach in Miami a lot (NOT family friendly), Sandestin just bit of a drive from Ft. Walton, San Diego, San Francisco, LA and South Padre to name a few. These are quickie get aways via air.
IF you want to stay in this area, we go to Sneaky Pete's on Lake Lewisville and watch the boats, listen to music, etc. Sometimes they have activities for everyone. We also frequent our country club pool which is great and family friendly for our 13 yr old.
As for swimsuits, no idea. I order mine from Victoria's Secret.
Welcome to TX!