The geometry package allows one to switch your layout mid-document. So, you could set it as twoside for the first two pages, and then switch to the default ("oneside").
Here is a minimal document producing four pages, the first two are twoside, while the last two are not set in twoside mode, as shown by the showframe option to geometry.

\documentclass{article}
\usepackage[showframe]{geometry}% http://ctan.org/pkg/geometry
\usepackage{lipsum}% http://ctan.org/pkg/lipsum
\begin{document}
\newgeometry{twoside}% Switch to twoside
\lipsum[1-10]
\restoregeometry% Restore to oneside
\lipsum[11-20]
\end{document}
lipsum was merely used to produce dummy text, Lorem ipsum style.