You can mix and match your proteins. My first venture on the weber with the paella pan was a simple chorizo and chicken dish using sazon (the poor man's saffron), more typical of a Puerto Rican arroz con pollo.
Some restaurants assemble their paellas at the last second, so you can make one for both you and your wife and then add your cooked mussels and clams to just your plate. When you take the paella off to rest, put your shells fish on the grill in a small foil pan (cover with foil to speed up the process. Pout the liquid right into your plate.