you wont have any problem launching at o-darkity dark. they usually have the gate open an hour or betterbefore sunrise, if they even closed them overnight.
Thats been my experience the last several years.
Who knows, maybe since Mukilteo bought the park, they manage it differently now? They sure did Jack the launch fee up high enough. $10.00 now, and new ticket machine that accepts debit, visa, and bills.

They had better fix the place up by next summer for that price!