Unvaccinated Nieces...

So I'm due in August with my first baby and the whole family is so excited, but my Husband's sister is an anti-vaxxer so her 2 daughters that will be 3 and almost 2 when our baby is born are completely unvaccinated. My husband and I feel that vaccinations are extremely important and do not want anyone around our baby who is unvaccinated until our baby is at least a year old. That being said my Husband's sister is a very sweet loving person and we are having a hard time finding a way to tell her this without crushing her feelings and making her angry. We have respected her choices in raising her girls even though we disagree with her on nearly everything. But now that we have our own baby to think of we are going to have to confront her and I know that she has never considered the impact her choice makes on other people and she's going to take it as a personal attack. Has anyone else gone through a similar situation or have any advice on how to have this conversation with her?