I think that shouldn't cause problems, even if cron was told to run the script between 2am and 3am. If you shut down your machine between 2am and 3am on a normal day (not on a day when dst setting occurs), cron will run the job scheduled to 2:30 when you next start it, that is, at 3am. I don't know how exactly cron works, so DST setting may be different.

(By the way, I think that here dst setting is from 2am to 3am in the spring, and from 3am to 2am in the automn.)