My personal opinion is to avoid complication whenever possible. For this reason I would agree that #2 is the better way. I've seen all levels of SB+ programmers find creative ways to include BASIC, simply under the assumption that there must be some BASIC somewhere, when really it's necessary only when it's necessary and a waste of effort otherwise.
The simplest approach here is a screen using ordinary field definitions just like any other screen, and if you don't want to prompt for the key, use the Key Source (if not Inp) as that's what it was designed to do.
So the only advantage I can see to the work field method would be the fulfillment of some masochistic fetish. Otherwise, there's no reason to work that hard for a simple result.