K.K.
Why are you putting him in a preschool? Socialization? Structure? My concern would be him being in a 2 year old room when he is 3. Unless he is delayed or lacks in maturity, he needs to be with the same aged peers. If there are other 3's in the class that may be okay, but a 3 year old room and a 2 year old room are totally different. Not sure this helps. If you have questions let me know...I worked in daycare 4 years and have taught preschoolers with special needs in Keller ISD. Good luck with your decision.
K.