hakodate to matsumae 5th may

Hi, I'd like to see the blossom at Matsumae castle, but I think the only day I could do it on is 5th May, which I know is one of the busiest travel days in Golden Week.
To do this I'm planning to stay in the only Hakodate accommodation available on 4th (hostel), and get up as early as possible to get to the station and catch a train to Kikonai, put my case in a locker, and head to Matsumae by bus (hakobus?)
I'm concerned about locker availability as I'd need a large size for my things, that's why I'm looking to get there early, around 7am or so.
I'm having trouble working out the bus timetables from kikonai to matsumae, could anyone help me out? Or even from hakodate to matsumae.
After seeing the blossoms I need to collect my things from Kikonai and head straight to Hirosaki or Aomori.
Are there many large lockers at kikonai station? And would I need a reservation to catch a matsumae-bound bus on this busy day, if so how could I make one?
I arrive in Japan on 8th April but don't reach Hokkaido until around 25th.

Thanks, Louise

If you take the bus to Matsumae from Hakodate there are more lockers in Hakodate station.

http://www.e-matsumae.com/tairyo-bus/bus280326.pdf (bus schedule)

http://locker1.exblog.jp/20665739/ (lockers in Hakodate station)