We could have a marriage advice, message in a bottle set up where guests can write on pieces of paper and put it in the bottle for us to open later. I have some large vases and we would just need sand, rope or twine, and some message paper.
Nautical Wedding Card Box, Beach Program Box. This box is great because it can serve multiple duty - at the wedding shower, for programs at the wedding site, and then for cards at the reception site. I love the nautical theme that ties in with the flower girl and ring bearer items too (see other pin.) Who knows - maybe you can have someone offering a demonstration of all the different ways to tie knots at the reception? (Other than the way you already tied the knot earlier in the day....!)