Yes you can add multi-site later if you want to. It’s slightly technical but not too difficult . Here is a link to instructions http://codex.wordpress.org/Create_A_Network. I will be doing a tutorial on this in a couple of months :)
There is also no harm in installing as a multi-site but only running your site as 1 site to start with.
I have a further related question. Is it possible to have a separate domain name for the web page & each blog? Viewers could then either go through the website to each blog or direct to the blog using the separate domains.