Adjusting cats to twins

Ash • Happily married and blessed to have welcomed our TWIN BOYS via IVF a year ago in March of 2017! 💛🔬🍍👶🏼👶🏼
I've read a few articles on how to acclimate cats with newborns. We have 2 male cats and in 3 weeks we'll have twins boys joining our family! Is there anything I should do before and after babies are born? I've let them roam and sniff the nursery with supervision. We had some issues when I become newly pregnant and moved their litter boxes out of the guest room. Let's just say, they did not adjust well at first and thought we would have to get rid of one. Now, they have adjusted to their new litter box location and seem very curious about the Rock and Play, MamaRoo and cribs. Any advise from experienced mamas of pets are very much appreciated! 😊👶🏼👶🏼🐱🐱