Should I use Multisite?

I’m building a site for a small nonprofit I volunteer with. I’ve been researching whether it would be wise to use Multisite for two days now and just get so much contradictory info.

I’m hoping if I list how I need the site to function, that I’ll get some good advice.

1. The public face of the website will be pretty straightforward charity site stuff. It will have a donation area that uses an e-commerce plugin.

2. Translations. We’re a literacy organization and teach quite a few Spanish and Russian speakers. I need several pages to offer translations to these languages.

3. I need a member-only section for the organizations’ board members and staff. It will have protected documents with the ability for users with permissions to upload and download documents and interact with a private calendar. It will also offer staff the ability to access our volunteer and donor databases.

4. I need a volunteer-only section with forums and your general Buddypress and bbpress and allow volunteers to post blogs that will go on the publicly viewable blog.

Should I use Multi? Will a single site do the trick?

I also need our staff to be able to handle the site’s maintenance and content changes.

Many thanks in advance.