Go with the lap quilts but make them obviously a set with some theme, fabric or color in common. Mama (a child of the depression and a trained nurse) instilled in us the necessity for planning ahead even if (especially if) facing tough realities is involved. Here's what I see in the case of a 50th anniversary quilt gift.
There is a real possibility that one mate might have to be hospitalized, rehabbed, etc. and the other serves a supporting role. I can see the love when both are using lap quilts in such a scenario that obviously go together. That's just one thought beyond regular home use down the road. It isn't always pleasant to think like this but I have been grateful to Mama MANY times that she trained us to face (and plan ahead for) the possibility of difficult realities.
Yes, I vote for a lap quilt "set" for the lucky couple!