Luxating Patellas and Agility?

So, one of my aspirations for Stella when I adopted her was to do agility training, and hopefully get good enough to compete. We started some and she knows how to use several pieces of agility equipment and really enjoys it. She loved it and I thought most of what we needed to work on was her recall and responding best to me instead of just running off!

However unfortunately a few months ago we found out Stella has luxating patellas. Though it feels silly saying it, it just sort of felt like that literal moment of dreams crashing to the floor. I feel like Stella is really sad about not doing that training anymore, and she will actually watch agility competitions on TV with great focus. We will still occasionally do some of the equipment at the dog park, and we have a little home course we'll probably use a little bit once the weather is warm. But when I went to Westminster to see some of the agility this weekend one of the women we knew (who runs a school for it) implied that Stella might still be able to do some. I'm a bit...on the fence about this. I do know the idea of us COMPETING in agility is shot but...do you think some agility for fun will be harmful? Like maybe some classes here or there? I'm just really worried about making her lame at such a young age.

On top of that it really sucks that she's such a high energy dog but I'm nervous about stressing her legs too much. She really could run all day, but I get worried about what that might do to her. Our vet did say "just let her be a dog" but I'm not sure how far that extends. Does anyone have any thoughts on this? Or on any physical activity we can do that's not too...physically taxing?