We did Kidcot in May/June. My five year-old loved it. Cool thing is, its free. At least, the mask is. The passport costs a few bucks.
As one poster said, some of the stations are a little hard to find. If I remember correctly, the Japanese Kidcot station was toward the back of the country's showcase, near the displays of the tin toys.
For an extra treat, have your children memorize "hello" in the respective languages. Because of a song he learned in pre-K, my son knew "hello" in Japanese. When he gave her his passport, he put his hands together, bowed, and said hello in Japanese. The CM was delighted, and spent a few extra moments with him. Cool moment for all of us.
The important thing is, give your kids time to enjoy the experience. Because we were pressed for time, we rushed through a couple of the countries. Our five year-old just wanted to sit and decorate his mask.