Yes to bringing a change for you too. It is so easy to spill a drink on someone.
Don't worry about other passengers, we don't care about children fussing or crying, we are in your company for a few hours and you will never see us again. As long as you are not letting them run wild up and down, it is fine and part of travel.
Do board early, not last minute. You need to be able to organise your stuff above your head and it might be full by the time you board and you would have to squeeze your bags here and there.
The special meals are served first, but it also means, you will have to deal with the trays for ages. The kids meals are quite disgusting in my opinion. If Singapore has introduced them, the fruit platters on the other hands are nice and fresh.
Wipes. Bring double the wipes you think you need and a few plastic plastic bags in case there are accidents of any sorts, from juice knocked on legs to vomit. I used to bring two changes for the kids, and one for me.
It can get very cold on board. So have a extra comfy layer for everyone, A nice, soft and baggy jumper or a big wide scarf that can become an extra blanket.
Sleep sacs might be difficult to handle in tight spaces. Are blankets an option? At home, the kids will get in and out of the sacs once per night, on a flight it might be a dozen times per flight. I have done the solo trip with my DC for ages from when they were very little. A blanket is more versatile if they want to sleep in odd shapes, folding legs. The bulkhead seats armrests are fixed, you can't lift them, so kids can't sleep on your legs. The only way to lie down is forward for them, so since they are allowed, the inflatable foot rest is a must. I have attached a picture. I hope you booked a seat for the 18 months old.
It will be fine. And you are going home, every minute on board is a minute closer to home.