barely remembered story about a moose-like alien

There's a book one I remember very little about, that I probably read about 1979 but that I'm sure dated at least 10-15 years earlier, that I've never found another reference to.

I think it involved a boy and girl who somehow make the acquaintance of an alien that resembles an anthropomorphic moose (yes, really). There was some plot element about how the moose-thing could teleport them, but there was also some sort of shrinking force-field around them that they couldn't leave, possibly generated by the moose's antlers. The reading level for this one would have approximated that of the Mad Scientist novels, and the few illustrations were similar in style to those in the Mad Scientist books as well. I don't have too much more to go on, except there was a Roald Dahl-like tone to the book as well.

Help?