Learn English – less religious alternative to “the creation” when referring to everything that’s alive

Why not call it a frame or border instead?

Both my children, and my four nieces and nephews, all have 2-3 godparents each.

All except one of the godparents are also aunt/uncle to the protectee, if it were felt necessary to avoid the word "god". But despite the fact that all bar none of the godparents are staunch atheists, I don't recall anyone ever objecting to the standard terms godson, goddaughter, godparent.

So far as we're concerned, a godparent is primarily someone charged with taking "greater-than-might-otherwise-be-expected" responsibility for the child's development of a "moral compass". There's often an implication that the godparent is first choice for "adoptive parent", if the biological parents meet with disaster - but that's got no legal significance in the UK, so it's really just a symbolic role.

As @John Y says, for many today the god in godparent has no more religious significance than the x in xmas, or the christ in for chrissake. So I would cite the fact that we don't bother to popularise an alternative "secular" term as evidence that most people simply don't feel a need for it.