When I play this game I randomly ring a bell at various times throughout the duration of the party. I'll read out one of the scenarios and then award a small prize to the winner of that scenario (eg. the lady with the most grandchildren). This gets everyone chatting amongst each other to determine who is the lady with the most grandchildren. Often I'll bring a dozen red roses and award one to each winner as the night goes on. It doesn't have to be roses. It can be anything small.
Sometimes people don't want to spend that much for prizes and would prefer just one prize for the person who collects the most points. In that case (and you would need to have less guests than the number of scenarios to guarantee someone would have more than one point), at the end of the evening, the lady who won the most ring a bell scenarios gets that one prize.
The other option, if you only want to give out one prize is to give each lady a small slip of paper if she wins a scenario. She will then write her name on the paper and put into a draw. At the end of the evening you can then draw from the names of all those who won a scenario.
I hope that helps! Wendy