Flying United with 15 month old!

Hey everyone I need some serious help/advice/recommendations! I myself do not fly much but next week I will be flying with my 15 month old on my lap while I myself am 7 months pregnant. I did book a red eye in hopes he will sleep the entire time. What can I do to make this easier? Am I allowed to bring food for him or milk/water in sippy cups? I know they're are different guidelines when traveling with an infant just not too sure on what is ok and what's not. Thanks everyone!!