You said you prefer weekends, you said either April or May work best, now, what weekends are open on your calendar? These are the weekends that Matt Mullenweg currently has open on his calendar. If we have to, we'll have a WordCamp without him, but I think everyone will agree it'd be better to have him there than not. So, put a checkmark next to the weekends you're reasonably sure you'll be available to attend.
(You can select more than one option)