some options can be banana, curd, apple puree, milk biscuits ( not recommend in routine) don't worry about heating food. babies are not as picky and choosy like us adults :)

Since outside foods would have salt and spices it is better to use ready made baby food which can be mixed or just a jar which can be opened. It is not advisable to keep cooked food for long hours as it can breed bacteria.

till one year it is advised to avoid any salt or sugar for baby. so it is anyday better to cook from home and take it. incase it is an emergency and you just couldn't manage at all, then you can use food at the party because you should not keep your baby hungry. also, try some home.made cerelac or khichdi powder recipes. carry your bowl and spoon and request for some warm/hot water and prepare your baby's meal