I think it should be ok. They are probably out playing at home no matter how hot it is. When I was that age, even in high school, I would play my best ball games when it was hot. (don't know why, just did)
Just keep the water coming and make them rest between innings and set on the bench in the dug out instead of goofing around if it is still hot, but it should start to cool down.
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it ain't over til it's over...
Cancel baseball because of heat? Baseball is 95% standing around or sitting. If we in the Southwest canceled baseball games everytime it was 97 degrees and 35% humidity, we'd have no baseball. I say: PLAY BALL!!