Exercise Machine Elliptical

Hubby and I have a disagreement about whether an elliptical machine or stationary bike shop for the family. Mainly due to the fact that we can win our son too much weight for their age. Anyway, I think, would be the best overall fitness, is an elliptical machine is a better choice for the whole family. My son was sitting all day at school, so why would it have seats. What do you think? I think that the elliptical would be the best solution and the target your core and your whole body moves instead of doing the Elliptical because it burns more calories and improve overall fitness.