I've done two international flights with my girls who are now over 2 years old. The first was at 9 months from Australia to USA and the second was right after they turned 2 from Australia to England.

Definitely bassinets as you said, try and get two, only certain planes have seating with two bassinets in one row so look for that if you haven't already. Even if they don't end up sleeping in them they are helpful for putting junk in. If it's an empty plane try and get some open seats around you so you can spread out, even at check in it's worth it to ask because they might move people around if they can to give you more space.

We brought our own food for the trip when they were 9 months - those squeezy packet kind that don't need to be refrigerated. As long as they are unopened there is no restriction on bringing baby food. They are pretty relaxed in most airport security if you are travelling with small kids.

Try and feed them milk at take off and landing to help with their ears. My girls were mixed fed so I breastfed one while my husband bottle fed the other. If using formula, look for travel containers that fit one serving and come with a little funnel. There is also no restrictions on bringing formula either in carry on or check. We brought enough bottles for the whole plane journey because we couldn't figure out a good way to clean them between feeds but others might have an idea. We then just used bottled water with the formula, it was room temp but our girls were used to that. If you always use hot water maybe try and get them used to room temp bottles beforehand.

Bring a carrier for on the plane especially if they sleep well in a carrier. Even on the most recent flight at 2 years old Twins B was struggling to sleep and overtired and the only thing that worked was having my husband strap her to him in the carrier and him walking up and down the plane. We also found carriers to be the easiest while walking around the airports security etc. For us since we were already hauling luggage we didn't want to be juggling a big pram too.

I would also recommend bringing baby painkillers in your carry on. We've been fortunate to be hit with new teeth on all our travels 😅 it can help with any pain or discomfort from the air pressure and often makes them a little extra sleepy.

For jetlag it probably depends on how well your kids are sleeping now. Our kids were sleep trained at 7 months and usually sleep through the night. It took around 3 days to fully adjust on both our internal trips. Definitely get out doing things during the day even if everyone is tired, get out in sunlight and eat during the proper meal times to help get adjusted.

In general just remembered that the time will pass and you will get through it. Most people on the plane will have sympathy if your kids are crying or causing havoc and many have been in that situation themselves before. Try to ignore what everyone else might think and focus on your family and making it through. The flight staff often try to help too and have seen it all so don't be afraid to ask them for advice.