For Dapper Days you can get a room at the GCH for $259/night and PPH for $189. Good the week before and the week after Dapper Day May 1 2016.
http://dapperday.com/spring-2016-disneyland-ca
I called the convention reservation desk and told them I wanted to book rooms for Dapper Days at their convention rates :
714 - 520 - 5005
You also get convention rates on tickets . $305 five day park hoppers are $257 and only good during the two week period of Dapper Days. They have the dates that are valid printed on them.
I booked so early because there are only a limited number of rooms set aside for the Dapper Days convention and they go fast. We went for the Fall 2014 Dapper Day and we hit a hot weather spell where the temps were 100 to 105, miserable. So, we figured we would try Spring this time.