I see it on nearly every trip, families stressed out, kids and parents having meltdowns. It's not the happiest place on earth for many families. It's just stress and meltdowns from trying to do too much in one day walking around with their spreadsheet schedule in hand. We took my husband sister and niece family to MK and his niece stayed outside the Haunted Mansion with the baby. When we came out our niece was just laughing that she was just witnessing the early stages of a divorce from a husband and wife arguing and having a meltdown. We take family there and usually still only do one day, two days at the most. This was our niece first time visiting and we still didn't do a marathon visit. Some relatives still have a hard time keeping up with me even in my "slow pace" but that happens at our local mall as well. Some relatives want me to plan everything for them, but the ones who know a bit about Disney, I try to let them plan and take the lead. My husband sister and niece did not know anything about Disney. The niece called me before the trip saying her mom told her I was taking them to "Magic Mountain" but she couldn't find "Magic Mountain" Florida on the Internet. After I explained, she said her daughter loved Sponge Bob so can we see Sponge Bob in the park.

I love them! <3 Also, no matter what we plan, they have a great time. It was my husband's sister and the great niece birthday so we ate at CRT on that trip. I got them the glass slipper dessert for their birthday.
The time we did the 3-day trip it was my daughter's 3rd birthday so we got annual passes. We stayed at the SoG. So my kids were 3, 4, 12, and 13 on this trip. My kids were asking to go home by the morning of the 3rd day... they had had enough. After that is when we started going back for just a day once every other month. Maybe a couple times we did two days and stayed at a hotel. But we really don't stay at hotels or eat a lot in Disney. That was the only time we had Disney Annual Passes as well. We had Universal Studios before then, Busch Gardens after. We don't do annual passes anymore. Right now my daughter has a "Fun Card" for Busch Gardens that includes the Adventure Island water park. But she gets invited to go with friends all the time, so it gets used over the summer. Her friends parents will pick her up and take her with them for the day while I am at work. She's now 13.
You don't have to do a marathon trip. My very first trip to Disney was when I was in 9th grade. We drove from SC to my Uncle's house in Coco Beach, FL. We only went to the Magic Kingdom for a 1-day trip (no hotel stay). I was so bored following around my uncle with his 3 little kids on what I thought were "baby rides". Finally my dad let me go off on my own. I enjoyed MK walking around and exploring on my on and riding a few rides. I have fond memories, mostly of being on my own and not feeling like I was stuck with my young cousins. I still have the ring I bought in the Disney gift store on that trip.
So that is why I feel like it's okay to not do everything and skip a reservation for something else. Don't try to do everything. If the kids want Fantasmic, I would do that over a dining reservation. I think the kids would remember that better than Ohana. Some dining reservations take too much chunk of time out of the day when QS food is fine.