I was a little too. I was prepared for the worst thing ever...I was pleasantly surprised! I don't know if it was just because I was expecting it to be so bad or if it was good planning (I'd like to think it was my expert planning but I doubt it!). It may also be because I don't have babies or little kids. Both my kids are very familiar with Disney World and know how to take care, plus have cell phones. So I did not have to worry about anyone getting lost.
My best advise would be to plan. We avoided Magic Kingdom on the "BIG" days for the most part. We used morning EMH and rope drop the most and got the things we wanted to do done before our fast pass times when crowds and lines were the lowest. We set our fast passes for late morning/early afternoon mostly so we had the time before when crowds were lower to get to the other things.
I also think our dining plan really helped. I think the lines for food at counter service places were crazy. By the time we were through our table service meals (usually, unless we wanted a more leisurely meal) the people at the CS places probably were too. I mean by the time you decide where to eat, what everyone wants, stand in line and find a table (in some cases not even being able to look for one until you had your food), and ate your cold food, we were probably done with our nice sit down meal. While the ADRs with the FP+ seemed to be a lot of "appointments" to keep, I think the CS route would have frustrated us to no end! So, it would be my advise at that time of the year to go with mostly sit down meals that you made ADRs for.
And maybe the biggest (which is easier for us because we did have a longer vacation than most people can do) is to take your time and just enjoy being there with your family. If you're worried about doing/seeing it all, you're going to be disappointed. When we ended this trip, we did not know we'd be back in July so we were looking at the end of our vacation not knowing when we'd get back, especially all of us since Tyler will be starting college next year. But we had a great trip and I would not hesitate to go at that time of the year again in the future!