Before you decide anything, make a trip to San Antonio and Kerrville in the hottest part of the summer. Go to ranches. Learn about the feed differences and how horses and stock live. Having been moved as a teenager from California to Maine I can tell you exactly what kind of shock it was, and Texas is drier, hotter and spinier even than California.
Massachusetts to the Southwest must be one of the most dramatic climatic and social contrasts in this fair nation. Get thee out of New England, regardless of the trip’s cost. Leave your children at home unless you want their opinions about the move.
Snakes, regardless of their density, don’t bother people who grow up with them. We can recognize at a glance exactly how dangerous they are. You are from a place likely without any poisonous snakes and will have to learn some simple rules to keep your animals and children safe. I’m with @gradytb, that poisonous spiders are maybe a more frequent concern. Black widows are no joke.
The Southwest is desert. Even the scientists struggle to gauge the trajectory of drought, partly because drought is normal. I taught on the Mexican border in New Mexico for a year in 2015-16. They hadn’t had normal rain, i.e. their usual summer monsoons, for nine years. A rancher friend there had been feeding his cow-calf operation irrigation-grown alfalfa for seven of those years. The nine-year old thoroughbred gelding they gave me had never seen a puddle until the drought broke in the summer of 2016.
What do you know about the water supply in the Hill Country? Is there an aquifer? My mom lived in Kerrville for a decade, so I know the Guadalupe River can rage or be a trickle. Are there other options? Government is verrry different in the SW. Counties have way more power than towns. You won’t be phoning up the local select board member when you have a question about roads, utilities, emergencies, or schools.
One place for information about anywhere in the US is City-Data.com.
Like CotH, the City-Data forums are the best place for advice from actual humans, though.
https://www.city-data.com/forum/san-antonio/
Best of luck. I love both New England and the Southwest. Luckily, I like extremes.