Aluminum holds up fine in my experience. I like the Blackburn EX-1 (often on sale pretty cheap at Performance or Nashbar). It might be overkill for your use, but I wouldn't sweat that. I guess that depends on what you will be carrying though. Some folks manage to carry pretty heavy loads even for credit card touring or commuting.

Also, even in the very unlikely event of a rack failure you can do a temporary repair using tywraps or bailing wire and a splint from whatever you can find by the side of the road. Shouldn't be hard to nurse along until you can do some more permanent solution like replacing the rack or having it welded.

Edit:
BTW, the dry run is a fine idea, but I never bothered and didn't regret it. We loaded the bikes for the first time in the airport at the start of the Trans America. Personally I definitely wouldn't do a lot of riding on a loaded bike unless I had to. The idea of training with a load or doing extensive "testing" of loaded riding may work for some, but I wouldn't bother. Some middle ground like loading your bike at least once and going for a longish ride is probably smarter than what I do though