I have an ileostomy. Once you get used to living with an ileostomy, you can do just about everything anyone else can do. By that I mean, as long as you know your skin barrier is secure, you can do it all. With an ileostomy, you have to be able to empty it before you spend a lot of time doing other things, but that is as easy as going to the toilet to empty it. It is unlikely to interfere with any competitive event unless the event lasts longer than 3 hours. As long as you have time to empty your pouch, you are good to go.
I play competitive bridge, in which there are tournaments that last several hours. I make sure that my pouch is empty before it starts, and in the break, I empty it again. I drink plenty of fluids in between and my pouch is not the limiting factor in my game.
Don't worry about how your ostomy will limit you: take it as another challenge! You have lived your life facing one challenge after another. This is just one more that I am sure you will be able to master. And just think about how much pride you will feel when you figure out how to do it. I remain available to you in case you have any questions.