A.T.
I would start in the Fall, they will be at a great age. I would higly recommend Zion Luthern Preschool in Anoka. They have an amazing program, and the teaching staff in unbelievable. My oldest daughter went there for 2 years, and now my younger daughter is there 3 days a week. LOVE IT!!! My son will also go there in a couple of years. They do a ton of different educational learning and gets them ready for kindergarten, but still let them learn through play.
I am a kindergarten teacher, so I think they do a great job getting them started on the right foot for school! I have also taught preschool at others places, but would still recommend this place. Good Luck.