How do you say "both A and B", especially if A and B are different genders?

Hola Michael

As a default we use the masculine "ambos" even if it includes a female, for example:

Jane y Jack son buenos estudiantes, ambos sacan buenas notas. 

But you can also use this other structure to say "both":

Tanto Jane como Jack son buenos estudiantes. 

Here's a lesson on this usage.

I hope it helps.

Saludos

Inma