What sort of curriculum will the preschool provide? DD8 went to a Montessori preschool for about 2 years and I felt like the Montessori math curriculum really provided her an excellent foundation for later mathematics. Otherwise, we didn't really "do" anything intentional for math, but we did follow her lead and discuss math as it came up related to other things.
For example, when she wanted a watch when she was about 3 1/2, I told her she could have one only after she learned to tell time on an analog clock--so then for a few weeks we studied clocks and time until she had it mastered (including counting by 5, the concept of "quarters", and so on) and had her very own watch. (Ironically, her interest in learning to tell time was longer-lasting than her interest in actually wearing the watch once she got it.)
She also liked games like dot-to-dot puzzles (which are also fun when done backwards), or pattern-matching games of various kinds, or sometimes workbooks because she liked them. We also did not do much computer math with her until she hit elementary.
Oh, and coins and money, too. That is an easy one to do, as long as you make sure to pay for things with cash sometimes, not just use a debit card.
