I’m assuming the issue is that the nurse may not be dressed tzniusly.
My feeling is that the issue is not so much about whether or not he will have a hard time guarding his eyes later on, but about the fact that everything one sees even as a baby is stored in his mind on some level.
It sounds like a good idea to me in theory IF the person in question is really holding by this. You would only be holding by this if you thought of it yourself because the idea of your baby seeing someone untzniusly dressed repelled you and because you yourself are super-careful about tznius.
If neither of those things are the case, I would be concerned that this comes from an unhealthy place.