My dad got sick last week too, which is terrifying as he's in his 70s and "retired" last year only to go back to work in a grocery store 5 days a week because he got bored during the pandemic. Thankfully he tested negative and felt better relatively quickly.
If you book the room and buy tickets/memory maker on the WDW website, it should all link to your MDE automatically. Just make sure you're logged into the right account.