This birthday cake/cupcakes are for twins (one girl and one boy, about 9-10 years old) so I am looking for decorations suitable for both of them.

What do they have in common? Do they both like soccer? Or both love blue? Maybe you could just have the cupcakes match the decorations that the mom picked out?

She does not have a specific decoration or theme yet. She told me that was sort of "disco", so I was thinking of using circles in various sizes and check with her their favorite colors. Your suggestion of ask her what they have in common its a good one.
Thank you!!