You sound like me and your husband very much like mine. When we took our older boys for their last trip in Dec 2014 for NYE (our in laws offered to watch our then 18 month old DD) we were already talking about taking the family when DD was close to 5 -- so that brings us to current day and we are going in April. so in a way we started planning over 3 years out. Of course we didn't really talk about details much but to keep the momentum we were always looking at
youtube videos of rides, shows dining reviews to help us get an idea of what we must do on our trip. The real planning started 11 months out when i booked a 2 BR at Kidani (we are DVC so we could book our room them) then at our 7 month mark i changed part of our time to Poly. During our summer trip with the in laws we started talking and hashing out the dining reservations we want and again talking about our ride priorities, how many days at each park. Then 6 months out I made the dining reservations. At 100 days out we made a disney countdown chain and we rip one off after dinner every night- I feel since we started this the time has flown by. Having the dining pretty much set (I usually try to grab a few too many reservations and then cancel what i don't need). At 60 days our FP selection help to nail down our park times and cancel any unneeded ADR. Can't forget selecting our MB colors!!! Now we are just at 3 weeks from our trip -- I almost feel lost because everything in our planning is pretty much done. I will check as we get closer for any changes to park times (which did happen last week), any changes to show times and in another week I will start looking at the weather forecast to help figure out how we should pack.
I think what really helps get through the time by watching youtube videos -- tim tracker is great. He has been doing many resort tours which has been fun to watch as it almost makes you feel like you are there. Listening to the Dis-unplugged podcast helps keep update on changes that might be occurring or new things being offered. I think once baby number 2 comes you will be so busy with them that it will help keep your mind off of things. Plus once they get a little older and you figure out their routine then it will help with figuring out your pattern for your days -- knowing when they need to eat/snack/nap/bed time will totally dictate how your trip goes. Even with my 4 yo DD I initially planned way too much and have scaled back on things to make it more relaxed - knowing that she could go,go, go but that she will hit a wall and turn into a monster so i have tried to plan it around how she is doing.