The alternative is a light, fast-drying hiking boot, something such as Merrell's Chameleon Ventilator ($110; www.merrell.com). But, they really aren't a water boot, so while they can stand getting wet, you wouldn' want to dunk them and just leave them soaking for days. Nike's ACG Air Zoom Tallac boots ($140; www.nike.com) have a waterproof bootie and are made almost entirely of synthetic materials, so they wouldn't mind a dunking and would dry fast. They're also extremely light (just over two pounds per pair) and have an interesting "exoskeleton" that wraps around the shoe to add support. They'd be a good choice.
So, my take is that it all depends on how much ankle support you think you'll need. If your route takes you through several short portages that add up to the five miles, I'd say the Salomons would be perfectly fine. But, if they're mile-plus portages, consider the Zoom Tallacs.
Have a great trip!
Check out Outside's 2004 Buyer's Guide for more paddling gear reviews and advice.