Because you've only got Bridge, all you can do is send the xmp files. On his side, he will have to put them back in the same folder (or folders if you're unlucky) as the raw files, then in LR he'll go Metadata > Read Metadata from Files. That will overwrite any metadata or adjustments in his catalogue with the work you've sent.
If you did have LR, you would select those images in your catalogue, and do a File > Export as Catalog - you wouldn't need to tick the options for previews or negatives (originals). This creates a single file (lrcat extension) which you can zip and email so it's even smaller. He would just do a File > Import from Catalog to bring your work into his catalogue.
Sending DNGs is overkill (bandwidth and file duplication) but would work.
John