Be sure to get down to Seward - lots of stuff to do especially at that age. Do a Kenai day cruise - you'll see whales and other wildlife at that time of year. Check out the Seward SeaLife Center. Also Seavey's Iditarod tours outside Seward, though may be redundant with your cruise excursion.

I'm from Soldotna, on the Kenai.
Make sure to stop at the Alpine Girdwood bakery, it's on the road to Whittier.
You could stop in Copper River to white water raft, that's kinda fun.
There's a great bookstore in Soldotna.
On to Homer, take the Danny J to Halibut Cove, stop at Sister's bakery in Homer.
Make sure to step inside the Salty Dawg in Homer but it's a bar so I guess you'd have to take turns, being you have kids.
Stop at any coffee wagon along the road and order a Mocha Bean Freeze.
On K beach road in Soldotna there is a place called Echo Lake lockers. Buy the cheese.
It's great to just drive down to the beach anywear and walk it. Lots of sea glass and just nature.
Alaska smells wonderful, take it all in.

Definitely go to the Alaskan native life center outside anchorage. They have hit or miss performances from native peoples (often teens) doing dance or drums or story telling but they also have this amazing area out back with different types of native housing and you can get into and they have native interpreters telling you about it. The polar bear escape tunnel is the best!

There is a wildlife rescue place between girdwood and anchorage that is a nice place to visit to see animals. It’s basically a nice zoo so not that exciting but it will guarantee you see bears and wolves and such.

My kids that age liked both of those things. Sounds like you aren’t driving up to Denali, right? My kids really loved the Denali Bark Rangers (the NPS sled dogs).

My husband has a work event in Anchorage this summer and my 6 year old and I will be joining to make a vacation out of it.

We will have 2 days in Anchorage and then 5 days to explore before we get on a cruise in Whittier. We have rented a one way drop off rental car- Anchorage to Whittier- and have decided to spend the five days exploring the Kenai peninsula.

Our cruise stops are Glacier Bay, Ketchikan, Juneau and Skagway.

We are looking at a helicopter ride to a glacier for dog sledding out of Girdwood. We also like hiking, kayaking, biking, wildlife/animal encounters, local beer and food. Not interested in long bus or train rides.

I would love to hear any recommendations for things to do with a 6 year old in Anchorage, the Kenai peninsula, Ketchikan, Skagway or Juneau.