True, this Forum is not ideal in that it does not have email subscribe-to-my-threads functionality. But it does offer RSS and a My Profile page to locate updates to threads you posted in, so try those methods.
As for WordPress and your 10 users. I am very sympathetic. I think there are many uses of WP that are outside the "normal public blog", and I think the alternative uses should be supported as well, such as: company website, personal diary, photoblog, moblog, podcast, comic series, review collection, poetry collection, glossary, etc.
That said. Most of the regular WP forum people seem to be against the idea of Admins emailing Users without the Users specifically requesting it or signing-themselves-up. This is probably justified because, for the typical public blog, doing that would be considered Spam. Everyone's against spam and against using WP for spam. So there isn't an advertised way to email your Users. If there was, then a site with 1000 users might email them spam every day. (But they could easily do that anyway, collecting the addys from the Admin panel by-hand, so preventing this functionality seems trivial and silly anyway to me).
However technically it could be coded. There is 1 simple plugin Kaf made that will give you a nice comma deliniated list of the email addys of your registered users, then you can email them whatever you want. But since you only have 10, you can collect their email addys into a list by-hand in a few minutes, so that plugin wouldn't help you anyway.
In short, you need to gather up the 10 email addresses, and zap them a quick email when you make a post on the blog. OR sign up for FeedBurner and use their easy Subscribe By Email thing (you would have to help your 10 people subscribe themselves, but it's really quite easy, a matter of typing in their email addy and confirming the request by email). Or use some kind of Subscribe/Digest plugin that's out there already, and try to enter the Users yourself so they don't have to mess with it.
I understand if your particular users would never use RSS. That's how it is with some sites, that's reality even if you recommend the feeds.
Good luck & hope these thoughts help in some way