You can ride the Gondola at WP. And it's free if you have an Ikon pass. Otherwise you need to pay for it. The alpine slide is gone as of now. They are putting a new one in but it's not in right now. There's putt putt golf at the WP resort base as well, but it's not a great course since it's covered in snow half the year.
There are a ton of flat biking trails in the WP and Fraser area as well as more challenging ones if that's what you want (I can be more specific if this is what you want). A lot of people like biking the Fraser to WP trail and stopping at breweries along the way for a beer.
Monarch Lake is a ~4 mile hike around the lake that is mostly flat. You can always go part of the way and turn around. It's a beautiful lake and you drive right up to it. There are a ton of hikes in RMNP but unless you get in early, you'll need a timed entry permit.
You can fish in the Fraser River as well as the Colorado. Not sure there is any tubing (would be really cold), but there might be some outfits that will raft you down the CO.