Since traveling 18 hours (back from Australia) on a plane with a newborn and a two year old (many years ago)I've learned a few things about traveling with children.
Tip one: Give your child the appropriate form of Tylenol 30 minutes before take off. If you've ever travelled with a bad head cold and felt the pressure in your ears you know why those little ones scream- it hurts!
Tip two: Take snacks.
Tip three: Pack some quiet toys that you aren't too worried about losing. I make a run to the dollar store or some other similar place and pick up a few new coloring books, small toys, etc. Depending on how long the flight is I may add a nicer toy or two. Then I wrap them. At certain points through out the flight the kids get to open one present each. For instance they open a gift at take off, one hour in the air, during a lay over, etc.
Opening the gifts through out the flight breaks up the trip for the kids and gives them something to look forward to. I hope your summer trips are fun and happy!