Wouldn't bother concerning yourself with the kids pack, anyway it will just give you more stuff to carry, there's nothing in it suitable for that age. Plus I will be amazed if you are even offered on on any flight other than MCO, we've never had it offered on any other flight in over 7 years.
Crew have always been very good at providing help and assistance, and believe the heating of stuff is possible.
However, you need to go prepared for there to be somewhere near you a certain type of traveller in PE, you know the type, "self important, peering over the top of their Daily Mail, occasional semi-loud tutting and attention grabbing show of discomfort". Have broad shoulders/ ignore.

)
Sounds like you have flown before with the ankle bitter so you will be well versed in the drill of little and often sips of liquids at take-off and landing to help relieve ear pressure. At that age, we found stuff which they can play with to keep their mind occupied worked well, i.e. stuff they need to physically play with rather than just visual.
That extra bit of space does make the whole thing easier and subject to the crew on the day, you should get more support.
NH