On a collaborative site, the bar is always higher to make a change which differs from an opinion already expressed, compared to adding something that nobody else has yet weighed in on. So if the relationship link is already there, you know that there is some level of disagreement already, however small.
The first step I take in a situation like this is to create a section of the biography called ===Children=== in which I list the known children of the family with source, i.e. will, etc. Any children currently linked but not documented, I put in a separate section called "other" or something like that. That at least tells the user of the profile which children are real and which are not.
The second step is to actually de-link them. It's important to let people know that the de-linking has taken place and why, so I'll create a sentence like, "The following profiles were formerly linked as children on the profile of xxx, however, no evidence could be found of their relationship. If evidence is found of their relationship, they can easily be re-linked," and then list the children below, with their WikiTree numberf." I then copy the sentence to each of the affected profiles, and de link them. That gives the message that you're not opposed to the relationship, you just don't have any evidence for it, and the solution to the issue is not to argue with you, but to find the evidence!
The third step, unfortunately, I am finding I need to take more often -- I run into people who don't read the biographies, but just re-link the family members based on their own unsourced genealogies. So the third step is to work with the project most closely involved with the profile and have the profile project protected, to protect the profile from added family linkages being made.