Tony wrote:

We're think that this summer we'd have the sprinkler put in to accomodate
this, we'd put in metal edging to define the bed line, and then we'd mulch
the area heavily. Then after that we'd start incorporating plants
bit-by-bit.

Slow conversion is a good way to go. You can go at your own pace, and
not break your back, attempting to do everything at once. If the area
has grass or weeds, put down some newspaper and then top it with mulch.
The paper will disappear in short order, and won't interfere with
planting, but it will definitely help smother the weeds and grass.

We want to come up with a good plan so we don't wind up with something that
doesn't look right when we're done. Even at this early stage we're
concerned about making a big mistake.

Don't worry about making mistakes. There is no such thing in gardening.
I don't know a single serious gardner who hasn't moved plants around
to make their design work better, or to accommondate the needs of a plant.

I've put up a web page with a few (small) digital photos and a diagram of
what we're planning. If people would take a look and either post comments
here or email me, I'd be grateful.

This is more of a personal preference issue, but I think that undulating
lines look much better and far more natural than straight lines. You
might want to modify the center portion of the plan to not be a straight
line. Instead of starting at one end and working your way towards the
other end (for example), you might want to plant things that take more
time to establish and look good (like shrubs) first. I started off
doing the former, and now wish I had done the latter. If you're
planning on putting in things like paths, seating, birdbaths or
fountains, put them in first, and plant around them. That way, you can
plan for having say, something fragrant next to the bench, or having a
food source for the birds next to the bath.

I'm afraid I have no input on the kinds of plants that will do well in
your area, for those types of conditions. You might want to look
through gardening magazines and books to get ideas. Good luck.

Suja