Just play dumb.
You could claim they are personal effects of low to negligible resale value. The letter of the law is that personal items over 300 bucks of value can be passed without an import duty, but technically can't be sold for three years without paying the duty. Don't worry about it and be helpful if you get searched or questioned at the airport. They care a lot more about antiques, art, booze, things like that get import duties, not toy cars.
I race toy cars for fun. If I need to explain, you'll never understand.
If everything is under control... go faster.
WTB: Carpet racing in Arizona.
It is obvious and intuitive to the most casual of observers that RC racing is better than golf.