If you start with a female one, you start with muchas. If you start with a male one, you start with muchos.
In your example we have
Tiene muchas playas, montañas, tiendas y restaurantes.
Since restaurante is a male word, it doesn't change the sense of the sentence.
We can do an inversion like:
Tiene muchos restaurantes, playas, montañas, y tiendas.
But since there are more females than males, it's better to put first the ones in more quantity.
A more complex result is to have:
Tiene muchas playas, restaurantes, montañas y tiendas.
Here you have female, male, female and female. However since the first word was used with its correct genre, the sense of the sentence doesn't change.