If you are a US resident and will be travelling to Canada, here is the information:

Option 1 : Passport
Regardless of your age, if you have a passport, it’s the easiest way to travel between Canada and the USA. You show your passport at the border and you are good to go.

Option 2: You do not have a passport

For kids under 18:
1) a birth certificate, a certificate of citizenship or naturalization, a U.S. Permanent Resident Card, or a Certificate of Indian Status
2) a photo identification

For adults:
1) a Nexus card or an enhanced drivers licence

Note:

If parents are not travelling with their kids to Canada, it is recommanded that they leave a signed consent letter to another parent or the coach that allows that person to take their kid to the tournament in Canada.