I'm sure it's perfectly fine for the cats to drink from the same bowl as the dog.

Hey...both my kitties were toilet bowl drinkers (until, of course, the day Howard fell in, thus breaking himself of the habit). Flushed only, of course!! Luna still does it on the rare occasion one of us forgets to close the lid. And sometimes when it is closed, she'll get mad and dump out her bowl of fresh water I left for her (I have to keep the water dish in the bathroom, because it's the only room that doesn't have carptet) and then knock the dish across the room like a hockey puck. ....But long story short, both my cats have drunk from the toilet and neither suffered any ill effects.

So if the toilet doesn't hurt them, neither will a little doggy slobber.

After all, cats DO lick their own butts and eat such creepy, crawly, and flying things like slugs, spiders, and june bugs