Reaching 100 years in age is cause for a big celebration. Remember that people who have reached such advanced age are likely to be set in their ways regarding the flavour of cake they like. Be sure to make a cake that is the favourite flavour of the birthday celebrant.
Go for Gold
A gold colour scheme is in keeping with a celebration of the golden years. Place the cake on a golden tray and decorate it with fondant balls that are covered in gold lustre dust. Create marzipan figures that are symbolic of the centenarian's achievements over the last 100 years and again colour them gold and place them on the cake. You could also take a baby picture of the birthday boy and have it made into an edible picture that you can feature on the cake.
Ice Cream Cake
Chances are if you've reached the ripe old age of 100, your teeth are not your own. An ice cream cake is perfect for such an occasion because as it melts it is easy to eat for those who do not have teeth. Ice cream cakes come in a variety of flavours and you can easily create one in the celebrant's favourite flavour. Decorate the cake with berries and perhaps write the centenarian's age and name in berries. If you're not going to attempt to put 100 candles on the ice cream cake, think about a single gimmick candle that plays "Happy Birthday" as it burns.
If a favourite relative has flown in for this very special birthday, consider creating a surprise cake in addition to a real cake. Create a cake out of an extra large box that will be roomy enough for the surprise guest to squeeze into. Decorate the box with paint and shaving cream so that it looks like a real cake. The idea is that as the birthday girl is about to blow out the candle, the guest pops out of the cake. Be sure that your elderly person is strong enough to handle the potential shock of receiving such a surprise. Perhaps a little hint beforehand will help to soften the blow. Serve a conventional cake immediately after.
Be sure that the birthday boy actually likes cake. On your 100th birthday you want to have your cake and eat it too, but if you don't like cake then having an alternative would be good. Mousses, doughnuts and puddings can be moulded cleverly into a cake-shaped dessert that you can dish up in bowls or even slice, depending on the consistency. These can also be decorated like a traditional cake with candles. Choose number candles that form the number "100" or have fun and use trick candles that reignite after they are blown out.