if you are looking for a very affordable option, you might try Casa de Montessori. It is not far from Kensington, and much more affordable than other preschools I looked at. They offer prepare and aftercare at really fair rates, and only charge you for what you use. Which is really unusual, so there is no commitment to per or aftercare. use it as you need it.
Your child needs to be 2.5 and potty trained, but it might be a good match for you. They are having an open house Sat march 2nd if you want to visit.