There is no glaciers ever that you walk across to get to Lake Solitude by the usual hiking trail. But, it is possible to cross snowfields earlier in the summer that melt away as summer progresses.

We spent 3 hours not including the boat ride going in ( uphill to inspiration point and then pretty level in the canyon)and 2 hours coming out ( downhill coming back). That probably brought us almost to the fork but not quite. You can do as much or as little as you want just plan on a little faster on the return trip. There are moose in the canyon about 2 hours in.

I do not know that trail. However, the ranger stations can advise you about all of them. The station was closed when we went (late September), but they're open all around the park in summer.

It’s about 1/2 mile up a steepish trail. It would be tough for someone with medical issues, but pretty easy for anyone else, including kids.

Cascade canyon is definitely the better option but involves more ascent. I would recommend either taking the ferry across or park at trail head at north of Jenny Lake & walk in from the North which is much shorter than from Jenny Lake Lodge car park. The ferry both ways saves 5 - 6 miles of walking. I strongly recommend you go on the Grand Teton National Park website where you can get information on all the walking trails with distances shown. The canyon views are different than those from the lake & the lake route views can be seen from the road anyway. In September Inspiration Point was still closed but Lower Inspiration point was open but to get to the canyon trail after visiting the point & falls you had to go back to the ferry and up another trail from there. We did not go all the way up to the top of the canyon. We stopped after it became totally wooded 2 -3 miles into the Canyon.

People take the ferry across and then walk up to the overlook. That walk is nearly a mile but it is quite exhausting. Quite vertical. I am 51 but I've worked my whole life in physical work and I know how to suck it up. My 21-year-old daughter is a dance major and we needed to stop and catch hour breath a few times. Having said that, people of all ages make it up to that point including people who are probably in their early 70s and using walking sticks. Once you make it to that point the awesomeness of the trail begins. The grade is very doable and it becomes visually more interesting. Nature is about experiencing nature so give it a shot. Bring snacks and something to drink and probably sunscreen. Let the kids know that after you get to overlook it's easy after that point. As a father of four, I would have snacks and drinks that feel like a reward.