which lens would you use for a family portrait on the beach?

17-40 or 70-200 2.8? im going to do a family portrait for some friends of mine and i know the 70-200's abilities for portrait work but id like to use my 17-40 more. i guess i could swap them out as i go but im wondering what would be your first choice. also, i mat be doing some ocf with 2 speedlights if lighting calls for it.

I would probably use them both in a beach sitting. You will want to use the 17-40 to capture lots of the beach setting without having to get back too far. Don't get too close to the people as wide angle lenses can distort people when used incorrectly. The 70-200 is a very flattering lens for portraits, so you will use it as well, just in a different way. Bring 'em both.

use 17-40 only when you want to capture mainly background.
usually use 70-200

the longer the lens the more flattering it tends to be.