This is a crown jewel of the Juneau area and perhaps one of the most famous attractions that they lay claim to. We thought it was neat to see, we were able to talk about icebergs and glaciers with our son and really show him what we are talking about! This is a rarity, since most times you need to take a boat to get close to the glaciers up here.
The Visitor's Center was under construction, so we didn't stay too long. There are good scheduled programs to attend (we loved the one on American Dippers) and there is a bit to see, with a large gift shop. Otherwise, if you want to step out onto the glacier, you'll need to bushwhack down. Your best bet is to charter a flightseeing expedition.
Brave souls swim at the lake, but since it is glacial, it's chilly, even on a warm day! The beach and outdoor grounds are open later than the center and provide a great place for exploration and picnics.
There are ice caves that you can paddle to but use extreme caution as they can cave in. It's best to consult with the local experts if you're going to be doing some of the more adventurous sight-seeing here.
Overall, it's worth a look. Go early (or late) to avoid the tour buses. During the daytime with the ships in port they are pretty ubiquitous.
Mendenhall is one of the most accessible glaciers, making a good stop with kids. The hike to Nugget Falls at the base of the glacier is an easy, level walk, and rewards kids with a fun end destination of glacier views and the splash of the waterfall. Leave time to view the visitor's center and have the kids earn a Junior Ranger badge here!
We took the Blue Bus from downtown out to the Mendenhall Glacier and hiked to Nugget Falls. This was clearly the highlight of Alaska (aside from the cruise ship) for my 3 and 4 year old.
There was a tent set up outside the visitors' center and there were several volunteers explaining kid friendly exhibits (animal pelts, etc.).
We made the walk out to Nugget Falls. My kids enjoyed jumping off the small boulders on the edge of the trail and throwing small rocks into the large inlet of water by the falls and the glacier. They also enjoyed feeling how cold the water was, and I wished that I had brought them some gloves.
It was mid-morning in July and for a couple minutes we had the entire area by the water fall to ourselves. I guess everyone else was busy whale watching...
When visiting friends in Juneau for Thanksgiving, we were pleasantly surprised to find that Mendenhall Glacier is open year-round. We enjoyed a peaceful, easy trek through the snow-covered forest right to the glacier lake's edge. Nearby was a frozen waterfall towering over us at least 5 stories high. The lake itself was frozen enough that people were skiing on it, but I don't recommend doing so as glacier ice is very unstable. It was wonderful to enjoy the glacier without the crowds of summer tourists!