Hey John,
You shouldn't have any problems getting your robot through customs. Just explain that you're going to a high school robotics competition, and that you're not leaving anything in Canada. Just to be safe, you may want to have an itemized inventory of what you're bringing across with you, in case they ask. Also, an event flyer showing the date of the Ra-Cha-Cha event would be a good thing to have.
As for attending the Toronto Regional, the situation is the same for what you're bringing across the border. What's different is that you'll be shipping your robot, and as such it will clear customs differently. Since last season, GM Canada has agreed to broker all American crates coming to the Waterloo and Toronto Regionals. For more information, visit:
http://www.firstroboticscanada.org/site/node/778.
If you have any questions, just send me a PM and I'd be glad to help you out. We'd love to see Foley Freeze come play in Toronto.