Are you going to
Disneyland (CA) or Disneyworld (FL)? I realized I was assuming you were going to Disneyworld, but most of what I'm writing is true for either. What is different is whether you'll be dealing with Fastpass or Fastpass+. Disneyland does not have Fastpass+ (it has traditional Fastpass) and Disneyworld only has Fastpass+.
You can bring any electronic device that a kid would want on an airplane. What you do need to do is have them wear headphones/earphone or turn the sound off. Also, the devices need to be off during take-off and landing. So if that's going to be an issue, you might want to think about other distractions. I've been on planes with kids making noises while playing games/doing other things and unless it's unduly loud (i.e. shouting), it's not going to upset people. I think you're being overly paranoid about getting kicked off the plane due to noises/behavior of your kids. Yes it happens, but it's incredibly rare. It's just that the rare cases are the ones that make the news (if it wasn't rare, it wouldn't make the news every time). Since you haven't flown yourself before, is there any way you could do just a short flight somewhere by yourself (or with your husband) even just for a day or a single night? That way you have the experience of knowing what it's like to fly and have those nerves for yourself out of the way before going with the kids.
I would highly suggest bringing (or renting) a stroller and getting a "stroller as a wheelchair" card for your youngest since you say he has braces. You will walk miles, even if you don't notice it (fewer miles at DL than WDW, but still miles). The stroller as a wheelchair tag will let him use the stroller in lines as well as between rides. It doesn't mean he has to use it through lines, but it gives the option. You might want to also consider renting either a pediatric wheelchair or a larger special needs stroller (and getting a stroller as wheelchair tag) for the older kids to trade off on. Just having the extra space can make a difference for some kids with ASD. It means they feel like they have something "safe" to sit in while in lines. You should be able to rent either offsite at either park so that it will be delivered and picked up from your hotel.
I'd suggest checking out the sticky at the top of the board regarding whichever park you are going to and the new
DAS system. It may help when it comes to dealing with your kids and lines. The DAS allows you to get a return time for rides with longer wait times. This means that rather than standing in a 1 hour line, you can go wait somewhere else. The general principle is the same at both WDW and DL, but the details are a little different (at WDW you get the return times at the rides, but at DL you get them at specific kiosks).