Lots of views in previous posts. As a parent, I have always advocated that the highest class should be for the infant, as the bassinets are not that usable for a long haul flight and having the extra space of the suite or club would is worthwhile. End of the day, the happier the infant is that will be for the best.

other things to note
- swapping between cabins often is often frowned upon, with good reason, it is very disruptive even when you think you are being quiet
- you say you have booked and then ask the question, that could cause problems as some crew may demand you sit where you are ticketed. There are some issues with I believe taxes and base fare being different for children versus adults, and some people booking kids in the higher class and then sitting in those seats.
- children should have an adult with them at all times, in an emergency it just does not work to have parents traversing to another cabin to find their children.
- if you booked the kids separately, there may be an issue with unaccompanied minors - contacting BA to note in the reservation can help.
- let the crew know you are travelling together - not with an expectation, it just can help if they know and may wish to suggest a parent can switch, or make it easier if you need something from the other cabin - it is hard to divide hand luggage always accurately.
- you kids are young enough they will probably not mind one parent being in a different part of the plane. Enjoy that, they get older and certainly ours have had issues when a split cabin situation occurs as teenagers.
- if you are a family that would make the decision that the parents fly in a different cabin to the kids, I suggest you start that early. We did not an personally, I feel that while enjoyable it was a mistake, as they now have an expectation that do not have the income stream to live up to.

enjoy the trip!

KF