If, by "celebrate," you mean a child dressing up as a Disney character and collecting candy from neighbors, I don't see why a child shouldn't "celebrate" Hallowe'en this way. Beware the Genetic Fallacy. Having said this, emphasizing death, and the monstrous, and the demonic in celebration of Hallowe'en is, for obvious reasons, not something a Christian ought to do.
As one who finds watching sports rather tedious, I would urge fellow believers to spend their time in other, better, more stimulating pursuits. But that's just me. I can't think of any biblical grounds upon which to assert that watching sports on Sunday is verboten.