Hi, and welcome. I'm also from Austin, and I actually learned a lot from jimbethesda who commented above.
I'm here to highlight a few things:
1) It's helpful when asking for design feedback to share what you want to use the pool for. As TexasSplash said, some pools cater better to sports/volleyball, others for lap swimming, others for sitting/lounging/entertaining, etc.
2) In regards to the spa, as Texas Splash said, many people don't use them. My wife didn't want one and thought the added cost would be a waste, but she's come around to it. I will say, multiple realtors have told me that it's worth getting the spa for resale. There are buyers who just want a pool and don't care about a spa, but there are definitely buyers that will see a pool without a spa and immediately rule it out. Those that don't want a spa aren't going to penalize a house for having it, it has some value even to those who don't want it, but there are people who absolutely must have one. Now that our's is done, my wife actually likes it. The kid considers it a mini pool, and if my kid couldn't full on swim, I imagine we'd use it a lot more. I also think in Texas, around Thanksgiving, Christmas and winter, it'll get use. Our spa integrates into our outdoor kitchen where we'll have TV and other things. Finally, it also adds a visual component to the design, it's another elevation, with more stone/glass work, so aesthetically, they add a bit.
3) I have an almost 5 year old, I went 4' - 6' on mine. My deep end ended up being more like 6.5', but honestly, kids aren't going to be able to stand in a pool until they're much taller. You definitely do NOT want to go shallower than 3.5' or you risk knuckle dragging while swimming. I probably wouldn't go any less than 5.5 ft deep side, one to allow canonballs and another to just give you more volume. My neighbor's pool is only likr 4.5' feet deep and it's fairly small, it gets very hot in the late Summer.
Anyways, good luck and you've come to the right place.