If you do not know the sex of a child then consider holding a baby shower that has rubber ducks for a theme.
This visually pleasing and very popular motif can be used to decorate everything from the invitations to party glasses. There are a great variety of commercial products available to support this theme on the market right now including floating toys, glasses and liquid dispensers with ducks floating inside, rubber placemats, baby furniture and soaps. It is a very popular motif as it is considered to be uni-sex.
All of these objects make great ideas for decorations or favors that can be given away.
Furthermore you can also invent games to play using the rubber ducks as a theme. Consider having a duck race in a baby wading pool (which of course is also going to a present for the mom.
The color scheme of at a duck shower is usually yellow. Plastic or rubber yellow ducks are used as decorations. Put them in vases to support flowers and use them to hold place cards. A nice touch is to float a few rubber duckies in the punch bowl. You can also freeze small yellow ducks inside ice-cubes and drop them into drinks. It is also a nice idea to have yellow napkins and table wear and if possible.
Flowers such as daffodils, freesia and yellow daisies and bright yellow candles also suit this event. You can also decorate lampshades with big tufts of yellow feathers, yellow balloons and yellow lights. Nowadays you can even get strings of light that look like rubber ducks.
Another nice touch is to make a yellow cake that is in the shape of a duck. You can make a nice French vanilla cake or lemon cake and layer it with yellow gelatin or lemon pudding.
Let the guests take a rubber duckie or two home with them as a party favor. You can also get rubber erasers, key chains and soaps made in the shape of these ducks.