Any chance you'll be staying at the Grand Californian? They have historically sold same-day tickets to hotel guests, seemingly without limit. My stepmother has always gotten them that way, never buying them ahead of time. Last year I personally heard a guy walk up to the front desk and ask for a bunch of tickets (like 8 or 10, I can't remember the number but remember thinking it was a lot) for that night's sold-out party and the CM just cheerfully sold them. No mention of "Let's see how many are still available," etc. I don't know if all 3 on-site hotels do/did this, or if they'll continue to this year, but for sure GC did in the past.