A.
I do not think you are being overly cautious or over-reacting. I will add that we chose to go the nanny route (I had 2 under 2) as it was financially better for us, much easier for the children and family over-all, and know that they are 2 and 3, the nanny helps with preschool runs, takes them to classes that I choose (so they are still getting socialization, etc. If you've any questions about other pros/cons, etc., please feel free to send me a message.
Good luck!