Easels for signs?

Canvas is lightweight, but you can still use easels. However (to be safe) you’ll want to attach clear packing tape to the back of the canvas and loop it around the back of the easel (to secure the sign to the easel). Then the easel legs might need to be weighted down too. So be sure to have something ready to be used as weights if needed, because you don’t want any avoidable emergencies on wedding day. .

They're generally pretty sturdy and it would take extremely strong winds to knock them over.

I think you should be okay as long as the sign is well secured to the easel. If you're really worried about it and/or your venue has a tendency to get very windy, you can also weigh down the base of the easel. One way to do this would be to put each leg of the easel into a flower pot (or another kind of container that would blend in better) and fill it with something heavy, like rocks. If you go the flower pot route, you could put rocks in them first, but then put soil and flowers on top of them to make them more attractive.

I used easels for my outdoor wedding and had no issues with them blowing over. That being said, they were a heavy, gold metal easels. So that may have helped. We looked into other options like hanging, but then you run the risk of them blowing and swinging back and fourth. The metal easel worked perfectly.

Hobby Lobby has a heavier easel:

Here