Kids meals are they same no matter which cabin they fly in.
On my last few flights it's been Mac & Cheese, sausage & mash, chicken korma, spiral pasta, chicken nuggets. I always think it's the safest option to order the kids meals and then they can have one of the adults meals if they don't fancy it, gives a lot more options. I remember having to surrender my meal to a 5 year old last year who was eyeing up my thai curry, I had the spiral pasta.
We also normally pack emergency sandwiches (which are dumped before entering the US) but we're not this year, going to feed them in the lounge so that the plane is a snack rather than the main meal.
Edit: some more ideas:
Sandwiches are served for high tea later in the flight, they're sometimes not suitable for kids (cheese and onion

) so definitely pack some snacks.
They only do fizzy drinks for kids, if they like their blackcurrent juice then pack one of those super concentrated Robinsons juice bottles, they come in under the 100ml liquid allowance and will last you 2 weeks!