You can certainly peg multiple images on the same location in one action by selecting them in the film strip and dragging them to the location. I do this often. So there must be some other issue here. What are the symptoms? I have had the issue where it refused to tag images (even single) but that was due to the phantom secondary window problem on the Mac.
Thanks for your response. As a novice LR user (still on my trial subscription) I thought that once I had mastered pegging one image to a location on a map pegging multiple images would be merely selecting a set and moving the set. Not on my Mac. I tried multiple times and nothing happened. However, I searched the web and found that I could select multiple images and holding down the Command key move the selected group to peg them at the same location on the map. This works just fine.
Now, on to new things to learn about LR.
As well as the command key you can select a contiguous block of images by selecting the first then select the end image while holding the shift key. You can also select disjoint groups by a combination of the command key and the shift key. For example to select the first 4 and last 4 images of a group of 10 - Click the first, hold the shift then click the 4th image now hold the command down and click the 6th image then, holding both the command and shift click the 10th image. This will result in two seperate groups of 4 images which you can then peg on the map together.