u can bring milk powder no problem
on air u can ask for warm water from stewards.
in airports u can ask for warm water from F&B outlets.

during takeoff / landing, where we usually experince pressure difference in our ears...

give baby / infants something to drink / chew. as the act of swallowing will balance out the pressure in our ears.

i give good branded chocolates to my kids. chocolates hv endorphins, that helps ppl to relax. usually i go for cadbury / ferrero .

for my 6 years old i always hv a back pack, with her, she carry it herself. the bag is filled with coloring books and lotsa crayons and colored pencils.

as for my 3 years old. his back pack is filled with his toys....