That's the right approach, IMO. Glad to see apps giving users more choice.
One thing to keep in mind is that, as per the current zap spec, if a receiver LN addr supports zaps, you cannot (should not?) allow both a plain LN tip and a zap to that recipient. So by offering users that choice in the app settings, you're going against the current spec :)
Which only makes sense, your approach is the sensible thing to do.