I would suggest that, as the 17th, a Friday, is unusually Disneyland-centric, many of us would like to spend more than our customary DTD-to-Disneyland ratio inside the Park itself for birthdayness.
And on the
18th, Saturday, a day likely more convenient to people lacking APs, and a day when the entire out-of-town contingent will finally be assempled at the Disneyland Hotel, we have a bigger Downtown Disney/Resort meet-up.
And then Sunday brunch in Topanga Canyon.
Sounds like a weekend to me!
