Personally, I would go with mom in Alberta and just say sorry but you can't make it, if you do not want to go. I think that parents forget that we operate as a business and invite us to birthday parties because they consider our children to be friends since they spend everyday together!!! For toddlers, their daycare peers are the natural choice for parties! It is much easier when the kids are older and have dropoff parties where the parents don't stay, then the kids can be friends without you having to blur your business relationship.