I posted this on a previous thread with a similar question recently:
From experience:
I’d avoid the bulkhead seats unless you are certain of a toddler seat. You won’t get a 15month old in a bassinet. The armrests on the bulk head seats tend to be fixed so it’ll make it difficult for them to sleep on you.
Encourage them to walk around the airport before the flight and tire them out as much as possible.
If you have a carrier then that’s a really easy way to board the plane and keeps your hands free for your carry on bag and your passports/documents
Don’t board at the beginning - you want to spend as little time as possible on the plane
Nappy change before you board - nappy changes on a plane are not easy. But with that in mind there’s usually a toilet that’s slightly bigger and easier to use the change table so ask the flight attendants if they don’t already point it out to you.
Change of clothes for you all - just in case!
All the snacks and a sippy cup to encourage swallowing during takeoff and more so during landing. If you’re breastfeeding then that’s perfect for take off and landing.
Some new toys - get them out one at a time. Don’t be afraid of a little screen time, especially if it’s not something that they are familiar with. Although we had a similar thought process and our little one just wasn’t interested!
Please don’t use a lollipop as a PP has suggested, it’s a huge choking risk
The jet lag can be hard on you all, but it is what it is.
And finally, don’t worry if they cry or make noise. They’re a small child and you’ve every right to be on that flight. Plus it’s unlikely you’ll ever see any of the other passengers again.