You could make center pieces for the table or even the little giveaways that the bridge and groom give out. If your real adventourous make your own flower bouquets. You could also hire a distant family relative to video tape the day.

Why would you have to pay for the wedding?

Two kids, one wedding is a solution.

(It is honorable to pay for kids wedding, but only do so if you have the cash saved up for it)

Try to find economies of scale, if this is possible. Could you negotiate with a photographer to offer a lower price if you hire him or her to do both weddings? Same for cake, same for florist, same for musicians, etc. If you are paying for the liquor, you might definitely want to supply your own, since what is not consumed at the first wedding can be used again, and you would not have to pay by the bottle, whether it is all consumed or not.

Whether one wedding, or multiple, the most effective way to save money is to develop a budget and STICK with it. Do not be swayed by the appeal that will be made to your emotions by all the bridal/wedding providers. ("it's a once in a lifetime event," "you only want the best for your child," "this will make the wedding truly remarkable.") Focus on the joy, not the glitter, of the occasion.