We didn't take the excursion so I'm sorry I can't answer the question.
As for the M&G with Mickey and Minnie, we were told to be ready at the Concierge Lounge before 1pm. I believe that's the time they expected to reach & stop at the glacier. Then, we were escorted down to the officers deck on deck 7, right under the bridge & the fitness. There were some treats, hot chocolate, and blankets. At around 1:30pm, Mickey and Minnie showed up and took some pictures with the concierge guests. They were there for about 20 minutes and left after everyone got a round or two of photo op with them. I'm pretty sure that's the only time they came out. So it might help if you know the assemble times for the excursion. If it's before 1pm or before they expect to get the closest to the glacier, it's most likely you'll miss the characters M&G.