I'm with Alicia. Reptiles don't cause any damage such as a cat or dog. It's just the smell really, so if you have time, I would scrub down like no tomorrow.
I agree with you though, I wouldn't hide them or make any attempt to do so. If the landlord is going in, they will know whats up. You can't miss the smell of reptiles...
I would just be overly polite about the whole sitch. If he calls, I would apologize profusely and genuinely mean it. Just say you were honestly a bit worried about telling them about your reptile babies, and offer for them to come and take a better look at them to show there's no damage.
I think if you pay rent on time and they have no other issues with you, being polite will take you a long way and hopefully they are understanding.
Wishing you the very best of luck!