Hi EdNerd, and first of all welcome to WebmasterWorld :)
I think there are a number of things you could do to not only keep things nice and simple for your end users, but to also reduce your workload.
What I would do is try and centralize your content as much as possible. To do this I would only have one website. One way to look at this is four websites = four times the workload.
I would use your main domain, and have one main website where you can place all your content. This will allow you to concentrate all your efforts onto the one site. It will also remove the questions about duplicate issues.
Regarding the domains it makes sense in my opinion to have a small collection of domains purely to keep them out of the competitions hands. You can also use these for a wide range of other purposes. Simply redirecting them may be a good idea of any of the domains have type in traffic. It would also be important to have a good look on each site to find out what pages are getting good traffic. You would then set up a redirect to take that existing traffic to the new location on your amain website.
You can also make very good use of your local domain names for measuring advertising performance. Lets imagine you have a domain that gets no traffic. Set up the domain to forward all traffic to your main domain then use the "new domain" as part of an advert in a newspaper. That way you can actually work out how much traffic was generated through your advert.
I hope this gives you some ideas, and I hope other members will contribute their thoughts.