First, welcome! We moved here a year ago from the Raleigh/Durham area. My son is also 3, he'll turn 4 next month. Let me know if you'd like to get together sometime.
My son is going to Our Savior Lutheran preschool this year. It's on Virginia Pkwy in McKinney, near Hwy 75. This is our first year at that school, but we have friends who have been going there for a while and love it. Last I knew, there was a short waiting list (1-3 children per age group) for the 3-year-old classes, but they said they often have one or two cancellations near the beginning of the school year due to finances or people moving away or whatever. Feel free to give my name if you decide to check it out: B. Rayle (my son is Timothy).