If you're flying out this weekend, the grand floral starlight parade is this Saturday. Usually, getting there is annoying and parking is a bitch because the parade essentially closes off entire sections of the city. Parade route maps are usually published ahead of schedule. The only plus is that you can remotely add time to your parking, since you pay via the parking kitty app, if you feel like spending more time in the area.
Fleet week also happens around this time, so if you want to walk on and inside a few navy ships, you can. The ships themselves aren't big or spectacular (iirc the one I went on last year retrieved buoys), but it's still nice to do. There's also the fair (games and rides) that exists during the rose festival. The Saturday market by the waterfront is alright, if you want to browse art and clothing.
There is the rose test garden, if you'd like to look at several hundred flowers. There is a Japanese garden nearby in the same park as the rose test garden that I thought looked pretty nice, even if it's a bit pricey for what you get. Iirc, Bank of America cardholders get free admission to the Japanese garden on the first full weekend. A zoo is on the other side of the park, but I haven't gone there, so I can't attest to the quality.
Multnomah Falls is also nearby and is nice to look at. If you have an extra hour, you can walk up the switchbacks to the top of the falls. The stream is surprisingly small, for the amount of water pouring down.
If you want to spend 2 hours driving northbound, you can get close to Mt. St. Helens (the landslide from a few years ago wiped off a huge chunk of road that they're still fixing) and hike near the mountain. If you want to spend 2 hours driving southbound, you can visit the Tillamook cheese factory. Not much else to do there besides look at workers working, get a few free samples of cheese, and eat ice cream. That's about it for what you can do in the cheese factory. There is an air museum also in Tillamook, but they're closed because of storm damage.
If you're visiting Oregon for a longer time (assuming you want to return), drive down the coast. It's beautiful. You can also ride ATVs on the sand dunes down by Gardiner. The High Desert Museum near Bend had a lot of stuff to see inside for the price. Charter fishing in Astoria is expensive (and you have to download the government fishing/wildlife app and register online for a permit), but I thought the experience was worth it. The Columbia River maritime museum (near Astoria) was also pretty cool with the amount of ship displays.
