What terminal are you departing from?.
Use their online check in 24 hours before departure and choose your seats carefully.
There will be seat back tvs.
Your children should receive the kids packs, they're okay.
Would certainly bring along your own foodstuffs for the children. BA tend to serve the childrens meals not long before the adult meals arrive, meals overall can be nondescript. I'd eat before boarding if at all possible.