OK, I know this post may get long, but I want to guide you to some alternatives.
First, Garden of the Gods/Colorado Springs would not be my first (or second or third or . . .) choice of places to spend 4 or 5 nights in Colorado. Unless you're looking for tourist traps, there are a lot of other places in CO where you'll get the real mountain experience and that your children will enjoy more. If it were me, I'd head a little further west and settle in somewhere around Salida/Buena Vista. There are soooo many things to do there for families with kids of yours. There's rafting, lakes, biking, hiking, real ghost towns, amazing mountains, hot springs pools, interesting little towns and museums. As a Colorado native, this is where I take out of state visitors with kids when they come visit. Check out
Now this is Colorado for lots of ideas on what to do and where to stay. I know you may have booked something in Colorado Springs, but it's not too late to change. You absolutely won't regret moving to Salida instead and your kids will thank you for it. (BTW, the pull up to Salida is no big deal. You can also go up through Pueblo and avoid any passes at all.) From Salida, head south over the easy Poncha Pass and connect with what ever route you were planning toward the Grand Canyon.
Redwoods: There are several groves of Redwoods both coastal and somewhat inland. For a place to stay, you might consider Harris Beach SP just over the border in OR. Much cheaper to stay at Oregon SP's anymore (CA has raised their rates through the roof) and it's a simple drive to several of the groves in the Eureka CA area. I don't know where you're heading from here, but Crater Lake isn't too far.
Burns OR. I don't know what is there that has your attention, but I'd suggest staying in the Bend area instead. Some cool volcanic features that kids love, including lava caves that they can poke around in. Cool obsidian flows in some places (the stuff arrowheads were made of). If you go here, you can skip Craters of the Moon altogether, as it is similar geology, but with more trees in the Bend area.
As many have already noted, Yellowstone is great for kids, but keep them close.
