Mark, I see the following options for your situation:
1) Use Web Gallery Wizard, which has smaller images, albeit not as an elegant interface or navigation
2) Watermark images, which would further promote your club. You can either put a BIG watermark, which would make images "unusable" or a tiny watermark such that users may take your images use/share them, offering your club the potential of increased exposure
3) Resize the images in an external image editor before you import them in Shozam!
4) Lower compression level for all images so they look poorly
For 2), 3), 4) you can also use PayPal for nice high resolution prints or digital downloads. I would think option 2) is best since I find users want to see a sufficiently large image before they buy. Otherwise it is hard for them to understand if the quality of the image, of the focus, the expression on their face, etc. is really to their liking. You may want to test out option 2) AND option 3) and see which one will provide more traffic, exposure and sales.
However, if your upload bandwidth is a bottleneck, you may be restricted in your options. Maybe the increase in image sales will offset the cost of getting a high speed upload link? (if available in your area)