Hello. I don't know about if you can or not, since where in Texas may make a difference. I would take the time to write a hub on this, but I haven't the time. Sorry. Maybe in the future. However just a note on the subject. You need a Mediterranean climate. That is why they grow so well in Calif. I live near the Avocado kingdom = Fallbrook, CA. I picked 'em for bucks when in high school. You will need either two trees or a grafted tree - male and female required. Plus honey bees to pollinate them, they do the best at it.
But, not knowing your son's age, you can grow them inside with a glass, water, toothpicks and a seed. Then transplant to a indoor container. This does have success in various climates because of indoor environments. Maybe there will be more answers following. If your son is in the primary school age group indoor will be fun.