Perhaps you make it clear to them you fully understand how to process raw files and that they're for archival purposes, you want to 'future proof' your wedding.

Perhaps you make it clear to them you fully understand how to process raw files and that they're for archival purposes, you want to 'future proof' your wedding. Also add that you don't intend to buy prints. I'd still ask for a higher res set of jpgs too, I think you'll look through those most frequently in the immediate years.