Would you accept a geography text that explains to your kids that the world may be round and that the evidence suggests that the earth is not the center of the universe?
Ideally, you should also tell the kids which evidence suggests a theory.
Elon Musk: The chance we are not living in a computer simulation is 'one in billions'
http://www.independent.co.uk/life-style/gadgets-and-tech/new...
Elememtary textbooks contain almost exclusively the seminal theories that we are very sure about. If we expressed our certianty there, kids might get the idea that all of science is similarly so.
In science, "the evidence suggests..." is a very high seal of approval. I'd place more emphasis on making them understand that than I would on adding a few nines to their certianty that the earth is round.