My wife and I were there for AP previews. We are both in our late 40s. We are in average shape for folks in their late 40s that spend all day on their butt's in offices (and now WFH).
We live in Houston but grew up in Louisiana. We are no strangers to heat and humidity.
Wearing a mask all day, especially in the afternoon in the parks, is very difficult. We did it of course, no complaints about the need for wearing a mask. I'm merely saying that at times it was VERY uncomfortable. At times we wanted to just take the mask off.
I believe that the requirement to wear a mask will negatively impact folks' experiences. If you are planning to go I recommend taking a 1 hour long walk in a hot part of the day to give yourself some idea of what you may face.
And plan times during your trip to just sit down in the AC and get a drink.