Keep checking online multiple times a day to see if something later comes up. Cancellations re-enter the system at all times so it's a matter of luck that you are online checking just as someone's cancelled reservation re-enters.
Also, the Disney reservation system has a quirk that makes it more difficult for odd numbered groups to get a res. Even though a party of 3 is usually seated at a 4 top, the system wants to fill every seat at the table so when you search for 3 you are often bypassed. Search for a party for 4 and something might come up. When you arrive at the podium just let the CM know there are only 3 of you. If it is a credit card guarantee restaurant you won't be charged for the "missing" person as long as at least one person shows up for the reservation. We're also family of 3 so we've done this.
Everyone who will be at the table needs to be included in the reservation so don't downsize to look for a table smaller than the total number in your group. It's easier to show up with fewer than to show up with an extra person and hope everyone will be seated.
Y&Y is a Landry's restaurant so if you are paying out of pocket you could look into joining Landry's select club. I believe one of the perks is priority seating. I'm not sure if this would work if AK is closing at 5:00 because I would guess it is dependent on what time the last seating at Y&Y would be.
If possible the restaurant will seat you even if you are late so you could show up at 4:00 and ask if you could watch the parade first.