Other mistake: Being a three time mom, I know that the sonogram that Susanne gives Nick at the beginning could not be hers, due to the fact that she just found out she was pregnant. The babies on that sonogram are too detailed. They have to be at least 30-35 week-old fetuses. At her stage, you would not be able to make out the baby.
Other mistake: When Nick fixes the doorbell, Kevin tests it and when he goes back to press it again, Nick pulls him back and doesn't make contact with the button but the doorbell sounds.