Yes, should be.
I use a rule of 90 minutes per meal. That works well if they seat you right away, with a later dinner you are waiting for other people to leave so you can sit. That means you may not sit at 6:25pm, it may be later. I would get to the restaurant 15 minutes before my ADR time and check in. That helps you get in closer to your time, no guarantees! Pleaset let your server know about your FP+ time, that way they know you are on a schedule. Maybe even pay for your dinner before your family is done eating that way when everyone is done you can just go. If you could move your ADR a little earlier I think you would be in the clear, the current time is right on the edge of my comfort zone!
I will tell you our bog experience
When I was in Disney, there were many complications with transportation, restaurants, and fastpasses. It takes a while to enjoy your meal, depending on what transportation you are taking, things could go wrong and take a little more time than expected. MK is very crowded during wishes and getting to the FP location will not be very easy. I had a breakfast at 10:20 and a fastpass from 11:15-12:15. When I was finished with breakfast, it took one hour on a monorail to get to my fast pass due to "technical difficulties" and I ended up missing my fast pass by 15 minutes-- but the CM was nice enough to let us still use it.
