Keep a book for the purpose and take it everywhere with you. Look at your collection of anecdotes from time to time and you will be amazed at how inspirational they are. I have a daughter who backpacked around eastern Europe with her boyfriend, having adventures; another who comes out with incredibly sweet and funny pronouncements -"A fossil is a memory of an animal who has died." And yet another who asks constantly, "What if...?" Her 'what ifs?' are always far-fetched and convoluted, a great starting point for a story.
These are just a few examples of many lovely family moments/stories which can be a starting-point for fantastic fiction.