It is never a good idea to tell your children to wait until they are older before you will answer their questions. When children ask questions, you have a chance to help them learn. It will teach them to come to you when they have other questions. If you don't know an answer, tell your child you will look it up and tell them later. You don't need to wait until they ask a question .
Many children never ask questions.
When our children were young, we didn't wait until they asked if they should look both ways before crossing a busy street, or whether they could touch a hot stove. Some things are essential for them to know. Learning about sexuality is the same. You need to decide what is important for children to know, and then tell them before a crisis arrives. A good time to start is after a TV show or news broadcast that deals with a sexual topic.