It wouldn't be so strange. It would be John who asked MC not to visit them and then, after being "convinced" by Hal and Jenny to allow him to visit his daughter, claiming that the day after that visit, they would confess to MC the whole problem related to the heart transplant for his aunt and what it will mean for his family and for him. To make sure it really happens, and at the same time be able to enjoy MC and Nicole's reactions to it in person, John would offer his house for that meeting.
Regarding the police interrogation, the police would have liked to talk to them after arresting Beeman to find out everything that happened, but Nicole's fainting and Chloe's condition happened, so it would be normal, taking into account John's influences, that the interrogations were scheduled for the next day. Perhaps the only person the police were able to question on the same day was Abi. That would explain why MC arrived before her to get Gavin and Nanci's ashes.
Well, the important thing and what I would like the couple to have. If it is through twins, it is fine, but it would also be fine if they have a boy/girl first, and two or three years later they have a girl/boy.