When the button is clicked, call a wizard which displays two options in a dropdown. Based on the option selected, you can call the method defined in the main class (in .py file).

For reference you can check convert lead to opportunity related code, where you can find multiple options while converting.

Hi,

Return a wizard from the button, then you can display your choices inside the wizard and then user can select from it and continue.

Return wizard from button:https://www.youtube.com/watch?v=QpzBdLWEWsE

Thanks & Regards