When shooting any sort of fast action, shutter speed is paramount -- it's the reason you've got shutter-priority mode. In general, you're going to optimize for shutter speed when you're shooting anything in motion, giving up ISO first, and then aperture if needed in order to get the shutter speed you want. This is where your compromises start, because a high ISO will tend to show more noise in your photos, and you may find yourself setting your aperture to maximize sharpness or to boost shutter speed rather than just worrying about the DOF you want (more on that in a bit).
The more you know about your gear, the better-prepared you'll be to start making these compromises. Understand how your camera performs at various ISO setting (probably starting around 800 and going up from there). Be sure to play with whatever post-processing software you intend to use so you can see what sort of results you'll get after noise reduction. Do some work with the lenses you're going to use. I'd take your 75-300, for instance, and do some test shots at 300mm, starting at wide-open and stopping down to see if there's a "sweet spot" for sharpness somewhere near wide-open. You're not necessarily looking for the sharpest aperture of all -- you're looking for the first stop where it's not awful anymore (because it's probably going to be noticeably bad wide-open).
Do some experimenting with focus modes. On your Canon, AI-Servo is probably best for following action, but it's worth playing with AI-Focus, too -- it'll give up focus in order to release more quickly. There are probably limited instances where this is useful, but again, the more you know about your equipment, the better off you'll be.
Now that you know the limitations of your equipment, it's time to start prepping for the event. The more you know about the game, the better your shots will be. You'll know where to look to find the action, and you'll be able to set up so shots come to you. This can be pretty helpful, since a nicely-composed shot with a little noise in it is going to wind up being a whole lot better than a super-sharp image of the back of the net (or whatever). Think about the sorts of shots you'd like to get, and make a plan to get them. You could be waiting a while if you're hoping they'll just happen by accident.
Finally, don't forget about the slower-moving scenes that tell part of the story, too. This might be of special interest to you, since you're going to be at a pretty fair disadvantage to someone with a high-end kit. Find the emotion in the game and find a way to capture that -- maybe it's the faces on the sideline when a goal is scored, or something along those lines.
If you do all this stuff, you'll find that your preparation also pays off when you finally decide to rent a lens, too. ;-)
[one more thing] -- Don't forget that "slow" is a speed, too. Every once in a while, you may want to choose a shutter speed that shows a little blur somewhere in the frame in order to convey action. Luckily, if you're in tV mode, so you'll get exactly the speed you're looking for in these cases, too.
