Don't count on your toddler being willing to eat airline meals and snacks! Little chewy fruit snacks work great during takeoff and landing for keeping his ears comfortable, and the different shapes keep him interested.
Look into purchasing some Goodnites. These protect kids from accidents (which tend to happen often while traveling) but are more underwear-like. They fit kids over 125lbs. Any kids who you are traveling with (especially in the car) should wear them just in case. It can really save clothes and car interiors in heavy traffic. Goodnites can fit kids anywhere from 3 to 16 years old too.
When traveling with children by air, if at all possible book at non-peak times (late at night, midday and Monday to Wednesday). This gives you a chance at a free seat for your child to stretch out and sleep. Arrive at the airport early. Sprints down an endless terminal are difficult enough, but nearly impossible when packing a baby on your back and holding a small child's hand. When traveling by car and you bring along "treats" NEVER give out them out too fast! Try every hour. You might even take a timer.
When traveling with small children, take along a package of outlet covers. Most hotel rooms neglect to provide these little shock savers, and there are often outlets placed tantalizingly at child height. For rooms equipped with stoves/ ovens, remember to bring knob covers, or simply remove the knobs while not in use.
When travelling with children, be sure to pack a change of clothes for yourself. Time and again my children have spilled sticky drinks all over me on the plane and I was glad I had thought to bring extra clothes for myself! Also it helps to premake airsickness bags at home as the ones the airlines provide are not always there. Another tip--put some cold drinks such as Capri Sun or juice boxes in your carry-on. If your child is thirsty and it will be a while for the drink steward to come down the isle, you will be glad you have them.