I've never heard of anyone having any problems ordering from a restaurant supply store. You can sometimes run into issues if it's a brick-and-mortar restaurant supply store, but you should totally fine ordering online.
Keep in mind that the restaurant business is hurting right now, so their suppliers are going to look for additional customers wherever they can get them.
On the very rare occasion when someone gave me a funny look while buying large amounts of messy items at a brick and mortar store, I always just say it's for a large family reunion, or that I'm picking it up as a favor for a friend who lives out of town. If the cashier had any weird thoughts (and we only think they do) they instantly vanish, as the explanation sounds totally reasonable.
Having said all that, I checked out the online source, and although the prices are great, the shipping is impossibly high. For example, six tins of chocolate pudding would run about $35 Canadian, but the shipping alone would add another $65 to that.
Haven't tried online ordering from them yet but shipping is always something to consider. If you can get the same if not more supplies cheaper in store why not do that if shipping cost go to high?