Most states (I believe there are only 2-3 exceptions) allow for a religious exemption and/or a philosophical exemption (just about every state allows for a medical exemption but that is based on reactions to vaccines or risk of getting a reaction due to health history). Now granted it's a bit stickier when you choose to selective vax and delay vax but a good ped should help you in that regard.

A religious exemption is nothing more than, "I choose not to vaccinate due to my religion" no further explanation necessary and if someone dares to try to ask you for a further explanation it's illegal. A philosophical exemption is quite similar but of course for those not wishing to go the religious route (although the supreme court has defined a religious belief within the context of philosophical belief so I would be perfectly comfortable using one or the other).

Anyway, long way to say that nothing, not even school or daycare (as long as they receive even 1 cent in government money or subsidies) can require that you vaccinate if you employ an exemption. It's your right as a a parent and a handwritten note should suffice. But as a parent who chooses to deviate in any way from the norm it will fall on you to know your rights because often officials will try to infringe upon those rights until you let them know it's not allowed.