So I was thinking that with our first, we did a lot of research and toured a lot of offices before picking DD's pediatrician (and after we picked they sent us lots of free stuff, yay!) This time, no one has mentioned the pediatrician. Do we just call and add a 'plus one'?

Also, I thought this might be a good place for FTMs to ask any questions they may have before picking a doc.
Re: Picking a Baby Doctor
I go to a family practice clinic associated with the major hospital in town. The clinic had me select from their OB/GYNs when I got pregnant, since my PCP at the clinic doesn't do OB. I had seen one of the doctor's on the OB list when I had had a same-day appointment for an urgent problem, and I had liked her a lot, so I picked her. She also does pediatrics, so baby will stay in her care going forward; they did ask me about this recently to confirm my choice.
My big thing with pediatricians offices is that they require patients to adhere to vaccine schedules; there have been outbreaks in my town due to low rates of vaccination and I would like to reduce LO's exposure to unvaccinated people as much as possible.
Since you're already established with that doctor, just give them a call and let them know you're having a baby due this December, and would like to have him/her seen by the same pedi as your DD.
That being said that is my #1 question to pediatricians offices. Then I look for their location in relation to my house/work and have narrowed it down to 2. I'll probably go in to have an informal 'consultation' with both and then decide based on how our personalities are. I'm looking for someone who will tell me straight up what to worry about and what not to worry about and I want to be able to believe them when they tell me. I also dont want someone who is going to talk down to me as I am an educated adult.... and is good with kids... phew thats a lot of things! I think its just a feeling.... and if it doesn't work out you can always change your mind and go somewhere else.
Married May 2014
DD born August 2016
Baby #2 due December 2017