\RequirePackage{xkeyval}

\def\@hello{Missing `hello' parameter. }
\DeclareOptionX{hello}{\edef\@hello{Defined `hello' to #1. }}

\def\@world{Missing `world' parameter. }
\DeclareOptionX{world}[default]{\edef\@world{Defined `world' to #1. }}

\ProcessOptionsX

\providecommand{\scenario}{%
  \@hello%
  \@world%
}