From last year - -
http://news.kirkwood.vailresorts.com...rticle_id=1815
Kirkwood Summer Operation Hours
Summer Activities
Kirkwood Mountain Resort will be open for summer on the weekends from July 7-September 2, 2012. Kirkwood offers a bike park, ziplining, ropes course and climbing wall, hiking, and disc golf.
Kirkwood tries to stay open for skiing thru the last weekend of April.
I doubt they have any services open in May. Maybe a caretaker and assistant manager.
A person might be able to make special arrangements - might.
A few places near the summit try to open for Memorial Day Weekend.