For Texas, here are the laws on kid seats:
He must be 4 AND 40lbs to move to a booster!
I plan to get my daughter the Graco Nautilus 3 in 1. She's 4 1/2 years old, about 35 lbs, & about 36." She is small for her age, but I want to keep her in a 5-point harness as long as possible!! Which for her, she may be in high school before she gets to switch to booster :) I am small, always was. I am only 5 feet tall & about 105 lbs. There are some boosters out there that would accommodate my size haha So that's why I say she will be in a 5-point harness for so long!