Can we dress for the ceremony at the chapel or do we have to arrive in our wedding attire?

You need to be ready and dress up before going to the chapel. It's quite a classy and magnificent place.

I'm pretty sure they have rooms to get ready in. They also offer tux and gown rental as well as make-up and hair services

No

You need to be in full attire. They do have several places on property to get wonderful pic & videos.