Keeping White Cloud Mountain Minnows in with axolotls is a 50/50 risk. Most White Clouds won't bother axolotls, but I do believe I've read threads about the Minnows picking at gills, or generally being annoying to the lotls. Personally, I've kept White Clouds in with my own 7-8inch lotls just fine, no aggression, just the occasional missing Minnow. So, I would say give it a shot but don't be surprised if more than a few turn up missing.
The fact that your axolotl has eaten such a large, wide goldfish does have me concerned, though.