Emily - a suspension post is a good idea but, for me, the position on beach cruisers is excruciating. You are so bolt upright that your butt and spine take all the impact. You can't support any weight with your legs the way you do with the Racer X or any bike with a forward leaning position. It's the same reason I hate the majority of "city" bikes. Plopping your butt on a bike and sitting bolt upright is just miserable. Not to mention, it's inefficient mechanically and your quads do all the work.

For me, a fully rigid mtb with fat tires would be tres good for what you're describing.

Just my 2 cents.