We are going for a week in May 2018 with DD6 and DS3 (everyone’s first visit). We plan on taking a break at the hotel each day we are in the parks to keep everyone somewhat rested.
While I would love to make it to a nighttime show everyday, it’s probably unrealistic with the kids, even with a midday break. Any suggestions on the top 1 or 2 can’t-miss shows? Thanks!
If your kids like fireworks (loud noises) than Happily Ever After is a must. Especially your first time! Illuminations is fantastic too, but my family finds it much louder. We haven’t done Rivers of Light at Animal Kingdom yet, but that sounds great, with no loud noises or fireworks. Honestly, just being in the parks at night is magical. As long as your kids aren’t melting down… then not so much. My advice is a long break in the afternoon that hopefully includes a nap. Poolside is fun too, but my kids are usually pooped (6, and 10) after a few hours in the pool after a hard morning of touring the parks.
Fantasmic at Hollywood. It’s seated, the kids will be able to see everything without having to jockey for positions every five seconds, and it’s usually early-ish. There’s a few “dark/scary”-ish scenes - BY DISNEY STANDARDS, but, I’d target it as a must do.
My daughter just turned 6–we have been about 6 times since she was born and never made it to the nighttime shows because she gets too cranky. We are hoping that we can do them this year and have two planned! I’ll let you know how they go 
My daughter is 6 going on 25 so I think she could handle the late nights most of the time but it’s hard to tell since Disney is nothing like a normal day. Let me know how it goes!
I think you have to know your kids and their limits … we’ve taken two trips with our three kids ranging in age from 18 months to age 6 at the time, and we kept them out late almost every night. They’ve always done well with no or minimal crankiness - probably because there is always so much to do and see! Staying late at the parks is one of the biggest reasons we’ve gotten a double stroller each time - much easier to put tired kids in a stroller and wheel them home at the end of the night as opposed to making them walk or stand in crowds for boats/buses/monorail. I agree that HEA and Fantasmic would be my choices if I was only picking two!
I’m going with @lfarley on this one, Fantasmic and Happily Ever After would be the two must-do’s for kids. Heck, we don’t have kids and they’re must-do’s for us! Fantasmic is probably my favorite nighttime show Disney has created. It’s starting to show it’s age a bit and is due for an upgrade but it combines the colorful fountains, pyro, lasers, and live characters all in one. It’s definitely a spectacle.