Network sites

I have two wordpress sites set up on one server which I did by editing the htaccess file

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /Family/
RewriteRule ^index\.php$ – [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /Family/index.php [L]
</IfModule>

This works fine however my client is now looking for a third site so my question is this – can i simply upload another wordpress site in a subdirectory and modify the htaccess file agin to take account of a third site or do I need to go down the multisite networks route. Also if i do go down the network route do i need to redo the second site?

Many thanks