If there is no street party near you when William & Kate get hitched why not invite some friends around for a drink and look at your garden.

You could always create a quiz based on what your visitors may spot as they walk around. Judging by the couple of photos I have selected it would be a quiz to find a seedy looking flower.

Homemade wine would be a great accompaniment. Elderberries, rhubarb, loganberries, blackberries, plums, rosehips, sloes and so on remain staple ingredients of home-made wine according to Homewine making .com

Pick a few flowers from your own garden to make an indoor floral display.
If the weather is bad you can ask people to name a flower beginning with a letter of the alphabet.
You could also select plants that would be appropriate for William & Catherine eg Sweet Williams, Lilies or wildflowers such as violets.