Personally I wouldnt have a bulkhead seat with a child of that age as when they see all the "space" they will just want to get out of their seat. I prefer to be "enclosed" as they then cant go far but it is squashier for you.

We travelled Perth-Hawaii when Gabriella was 18 months old and are going to Europe in August when Alex will be 14 months old. Personally we have chosen each time to pay for an additional seat for them as at that age (unless they are small) they really do get too heavy to be on your lap the whole time. Also there is never a guarantee that there will be spare seats.

Sultanas work wonders with little toddlers on flights as it takes them forever to get thru. Snacks, snacks and more snacks is what I recommend as well as some new toys/books/colouring in and a couple of familiar things too.

I would also recommend perhaps putting a spare shirt in your nappy change bag for yourself as inevitably you will end up covered in food or drink, especially if he is sitting on your lap.