I don't think you need that part of the line at all. You can just stop with: "Life was already hard enough without a little bit of pretend." The rest of the line feels redundant to me, and as it risks shattering a child's preconceptions, unless that is the point of your story, I wouldn't go there. Frankly, it's unnecessary based upon your setup from what I can tell. Now, if there's a later point to your story where you are going to prove the adult the fool for not believing, that's something you need to consider. But from your original post, I'm not seeing evidence of that setup/knock down.
One other thing I'll mention. POV. Exactly why are we getting to know the adult's inner thoughts here? Not that you can't do that, you can do anything that works. But be careful you aren't unintentionally head hopping here. (I don't have near enough text to see if you are or aren't or if this is simply a stylistic effect.) Is she one of your POV characters? Unless it's important for characterization that we know what Mrs. Sudbury is thinking, you can even cut out every bit after “I don’t know if it is true, but it might be." And you'd have much the same effect from the children's POV. (They aren't privy to her thoughts.)
Good luck.
