I did Cinderella's Royal Table in Nov 2016 with a then-seven year old granddaughter. We were brought in fifteen minutes after our reservation time and we were there for one hour and fifteen minutes for a total of one hour and a half.
I did Akershus Royal Banquet Hall in Oct 2017 with another then-seven year old granddaughter. We were brought in fifteen minutes after our reservation time and we were there for one hour and a half for a total of one hour and forty-five minutes.
Personally, I would book the FP+ at the one hour and a quarter mark after the ADR for time to be checked-in, relax and enjoy the character meal experience and then have travel time to the FP+. After all, the FP+ are for one hour so if it runs into your FP+ time fifteen minutes, you still have forty-five minutes but if you need to leave after one hour, the time can't be backed up.
Also one thing folks should be aware of when it comes to character meal. You paid for the character meal. It is your experience. Don't let the server push you into ordering before you and yours want to. Their instructions are to get you in and out but you are customer and if you have a fussing toddler (or child or adolescent or adult) that is over-excited and has no interested in eating, take your time. Let them relax, maybe have a cooling drink, meet a few charater and see how things go.
At the Akershus experience, my granddaughter and I just wanted to soak up the air conditioning and let the exhausted feeling from the heat/humidity go way before making any decisions. It took three times of telling the server this before he want away. But we did and he did and it made our experience so much better.