Dave,
I'm assuming for 19mm boards, you'll be using 6mm tenons.
If exposed tenons are acceptable, they can be the choice and will be marginally stronger than regular tenons in your case, as illustrated in Doug's post.
That said, if in the future you have a similar project that requires non-through tenons for aesthetics reasons, you can still do it with the procedures I outlined above using 6mm tenons (or 5mm x 30mm tenons). The trick is to cut the mortises just shy of 20mm depth (total), say 18mm, and use 6mm tenons that are trimmed to length.
To mill 6mm x 18mm mortises (9mm on each side), use spacers to restrict the plunge:


Regardless of what method to use, this "but Im going to do some practice joints and give it a go" is the best thing to do.