I know you from other boards. I'm due the 28th. ;)
I would start with the one that seems most interesting to you. CTG is not my favorite. I chose to start w/ it this year as I came back to MFW. It was not the best choice for my family as we weren't really interested in doing that time period. My kids really wanted to do RTR. School would have been more interesting to us this year if we would have began where we wanted.
We are looking forward to RTR next year. My second time through it.
My oldest is not going to make it to modern history before high school. The last several weeks of EX-1850 is a state research unit. I could have her start reading through SOTW 4 during that time and finish it up over the summer. OR I might do ECC. If I do ECC I will have her read through either two of the SOTW books or get an American history book to read through during that year. Another idea I have is to assign modern/American history readings in the summer. She won't mind this because she likes to read. My girls haven't done ECC. I know, from having done the MFW cycle before w/ my older dc, that they will need the knowledge of where places are and what the cultures are like, in order to fully appreciate what they are learning in history. It is not a deciding factor to me though. Interest in what we are studying is more important.
Anyway, those are ideas I'm thinking through for myself. I don't know what I will pick and will probably wait until to this summer to fully decide.
Blessings to you as you figure this out. Praying for you and your new little one coming. We are getting so close!