I’ve never had an issue buying Lightning Lane for Guardians…haven’t been to Animal Kingdom in a minute but I’d imagine Flight of Passage isn’t any worse than Guardians. I’ve seen Guardians LL’s available as late as 1pm in the summer and you’re going during a much slower time of year…I think you’ll be good.
You also don’t need to buy a Lightning Lane to get on Guardians. If you’re up at 7am, you can sign up to reserve a standby spot for Guardians (you’ll only end up waiting 30 minutes in line once your time is called)—this goes for everybody and gives no preference to on-property hotel guests. They’ll also release another round at 1pm…you have to be in the park to get that but, again, never had any issues even in the peak of summer.
Though Avatar doesn’t have a free reservation option, giving yourself three solo days at Disney will give you plenty of time to just suck it up and wait standby if you can’t swing a Lightning Lane. There’s not many rides at Animal Kingdom so even the worst line would fit snugly in a full day at the park.
Hope this helps! I try to pack in as much variety as comfortably possible every time I travel, be it for work or vacation. I’ve never once regretted seeing more than what I’m there for…so count me as a vote for checking out both resorts while you’re in town :thumbsup: