Most theme parks have strollers that you can rent if you really need to use one. As someone else mentioned, at age 7 your child should be able to fully participate in your activities. If he can't then maybe it isn't an appropriate thing to be doing with him at this point or you should consider restructuring the activity. At a theme park, break the day up a little. Go early in the morning, take a break in the middle of the day at the hotel and then go back in the late afternoon.
My parents traveled with us frequently at this age and younger- strollers were "out" by age 4 (ish). We each had a bag packed with things to entertain and feed us in-flight and in the airport. As a school-aged child, your son can use a backpack and can carry some of his own things in the airport. If you need to get b/w terminals quickly, ask for help when you check-in. They may be able to provide you one of the carts that they use for that purpose.
A friend of mine and I were talking yesterday about how once you carry a diaper bag, you feel like you can never go back to a regular bag again! If you are finding yourself carrying 100 "just in case" items, try editing and downsizing. Have him be in charge of some of his things and remember that in most cases, you can buy it at the park/airport/hotel. More costly, but do you need to pack 6 bottles of water?
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