The nearest place to buy quality discs to the Kelowna Disc Golf Course is at Fallow Ridge in Coldstream (just east of Vernon). The owner of this private course has a good selection and fair pricing. You'll certainly want to check out his creative course while you're up there. It's about a 1 hour drive from Kelowna. I believe you can find 3 packs of beginner discs at Canadian Tire and Sport Check but these likely won't be suitable for anyone who's serious about playing. Other options would be Kamloops and Vancouver.
The Knox Mountain course doesn't have any drinking water so you may want to pop into the convenience store just a few blocks south on Ellis. It's the closest store of it's kind.
Knox Mountain Park Development Plan - Info on the new 10 year management plan
British Columbia Disc Sport Society -
Courses, Tournaments, Tips and More
Professional Disc Golf Association - About,
Courses, FAQ, Videoand more
Calculating
Your Disc Golf Handicap
Youtube: Disc Golf Introduction
Youtube: Long Drives
Tips/Techniques
Youtube: Putting Tips/Techniques
Kelowna Ultimate Frisbee League