I was actually going to recommend the trail up past the Broome Hut. It's from the Second Creek trailhead (not much parking), very close to WP. The trail goes East to West up past the Broome Hut (which can be reserved but not sure how) and if you keep going, you can reach to the 'summit' at the end of the WP chair lifts.
Not bad. We did this in about half a day when my youngest son was probably 6. I wouldn't necessarily recommend that, we should have brought WAY MORE SNACKS, but that gives you an idea that it's a nice hike but not terribly difficult.
Also, if they're still open, the alpine slides at WP are a barrel of fun. Highly recommend. Some friends of ours said there's a zipline course out near Fraser that's also fun, we may try to go back and do this some future year. If you want to drive, I believe there are places in Estes Park you can rent a Jeep and drive on a 4x4 trail in that area.
The GAIA app is one of the better free apps to show trails and elevation, although it's pretty bare bones in terms of marking trails and trail suggestions. You gotta know what you are looking for first.