Best way to share photos

Why not use Flikr or something similar?

because my site is build with wordpress

Ah! So you already have a blog, yes? In that case you might want to have a look at some of the gallery plugins.

i have a wedding site that I built.

they also need to be able to download the image as well. Any ideas?

Any image on a web page can be downloaded by using the right click (context menu) in the web browser.

is there a way to have a download button next to it

Have you tried looking at some gallery plugins? Some may have this option built into them.