My family has food allergies so we rarely eat out and generally aren't used to the noise level in restaurants (any restaurants), so the MDR was really challenging for my littlest.
On my first cruise on the Dream with a 3 yo and 5 month old our dinner was taking 2 hours every night and we alternated who left the room with the 5 month old (grandparents were along too to get some rare time with grandchildren and it was only 4 nights, so no nursery that trip). It was manageable but not as enjoyable as it would have been without interruptions.
On the next cruise (kids now 4 and 1) on the Fantasy, we booked nursery time for dinner every night (5:30 - 7) for the 1 year old and never had wait too long for drop off at 5:30. We made sure we were early to the MDR every night and asked the servers to get us out of there as quickly as possible. Most nights we had desserts by 7 and one person went to pick up the kiddo while the other waited to place the food order for the next night (no grandparents this time). I was given a dessert plate to take back to the room once or twice when it was taking longer. With the 1 year old in the nursery, I felt like I could focus on eating my own food instead of taking care of two kids at dinner. That would still be a benefit for me even if we had been placed with other children.
The next cruise he'll be 3 so we're going to try having him join us for dinner again, but I was really glad I booked nursery time ahead for the one year old. I think you can cancel 24 hours in advance if you book it now and find out you don't need it (at least you could last year). That was my backup plan if I found out I didn't need it, but I definitely didn't cancel any