A study of children who were not hospital inpatients showed that they generally discover the truth on their own at the age of 7 years. Children reported predominantly positive reactions on learning the truth: 2 of 3 said that they felt a sense of pride in figuring out the truth about Santa. Half of them thought that even though Santa was not real, they liked the idea of Santa. Parents, however, described themselves as predominantly sad in reaction to their child's discovery.2 However, it is not until the middle childhood period (from 7 to 12 years) that children are able to think about Santa Claus simultaneously in 2 different ways: as a pleasing idea that helps them enjoy Christmas and as someone who is not real.
Santa is linked to kindness, although children might not like waiting in line to see him at the mall. Children often stop believing in Santa around age 7 and this bothers parents more than children. Just because some children stop believing in Santa does not mean he does not exist: some people do not believe in evidence-based medicine, yet here we are.
The child’s pantheon: Children’s hierarchical belief structure in real and non-real figures
In addition to testimony, content, and source information, we must pay more attention to the specific role that cultural rituals play in widespread belief of culture-bound supernatural figures.
The first article shows that your child will likely transition into a belief that Santa is both a pleasing idea that helps them enjoy Christmas and as someone who is not real.
Altogether, these articles suggest that you, as the adult, don't need to intervene with your child's beliefs about Santa, your child will figure it out, probably before they're 13yo, and as your question shows, you will feel some distress about this transition.
Additionally, regardless of the age your child figures it out, the majority of children continue to support teaching other/their own children to believe in Santa, which could be viewed as a cultural structure of belief in supernatural figures.