How to thank employer for considering late start date

I got a job offer, but couldn't begin on their expected start date despite me telling them I'd be able to do so during the interview. I asked them if we could push it back a weeks later, and they just told me that they were willing to do so. They mentioned two new dates and asked me how I would like to proceed. How should I respond to that? Could I start with "thank you for your consideration"? Or "thank you for accepting my request"? Thanks for your help!