I agree with previous comments,... if you do not have custody decision making powers to stay out of it.
I would be more concerned if the older step kids were getting shots and getting something from the shots and your baby getting sick(or from stool of other infants). I know that sounds strange, but after some reading you may see what I mean by that.
Books such as A Shot in the Dark, and What your pediatrician won't tell you about vaccines, etc. are worth looking into. Go to Library and look for books on Vaccines and immunization programs...look at British Medical Journal(Online). You will find that disease is not necessarily erradicated by vaccines, and that the scheduling is arbitrary, or contraindicative in the combining of vaccines, and potentially dangerous. That is why there is now VAERS- Vaccine Adverse Effect Reporting System.
Then there is National Vaccine Information Center...http://www.909shot.com/
Try not to judge older kid's mom...the kids are older, she may have great advice for you and your little one, and possibly a better pediatrician..you never know!
Be prepared for a battle and alot of scoffing once you see the other side of this Industry.
I personally object with my two older children, have to file with health department, and have a modified schedule for my toddler, as I have joint custody.
Some good articles on Mothering .com too.
Good luck, it is hard when ones you care about have so many influences, and you feel powerless...was a step-mom myself, had no rights over step-son, ...but feel that way about bilogical son with ex quite a bit too.
Docs do not know everything...had one want to cut my daughter's tongue, because he said she would not be able to talk...I refused,
haha...if you only knew my daughter!Blah blah blah...
Yak Yak Yak! Never stops :)
Try to relax, be open minded, and gather information from many sources in order to be able to make a more informed decision.
Great baby age! So fun at this stage! Enjoy.