The discounted tickets from the Edmonton military base (Edmonton Garrison) are indeed for real, and are still available to the general public.
What needs to be considered is whether obtaining that discount is worthwhile or not.
West Edmonton Mall has a variety of discounts built into its pricing - looking at the water park pricing - there is the adult full price, yes, but their is a child's price for $6 less, discounts for seniors, and those with disabilities. There is a discount for arriving within three hours before closing time, a toddler time program, early bird discount, and all day family passes.
So there are lots of pricing options available - I would recommend checking WEM itself first to see what is available for your situation before heading up to the base.