Then something like this in 2.8mm in the corner of each room to be monitored or 4mm if a full 90 degrees isn't needed and some clarity at distance would be good.
https://www.amazon.com/Hikvision-DS-2CD2432F-IW-Indoor-Camera-2-8mm/dp/B00JWCV9CU/ref=sr_1_1?ie=UTF8&qid=1475667757&sr=8-1
No PTZ but it'll cover the whole room with the wide angle 2.8mm lens.
For a bit more money this is a nice PTZ cam that'd really fit the bill.
https://www.ipcamtalk.com/showthread.php/9163-Dahua-Mini-Black-Face-PTZ-(SD29204S-GN)
Put 'em in a corner parked at wide angle to cover everything and they're still PTZs for zooming in on stuff when he's watching live.
Available in Wifi or POE (not both at the same time) so make sure he gets the -W version for wireless. Nayr's is the POE version without wifi. Put a bunch of them around the house on Wifi and prepare to be disappointed though. Too much data for wifi to handle reliably, plus the cams will probably kick out every time someone warms up their coffee in the microwave. He'll want everything recorded and the only way to do that reliably with a bunch of cams is for wired. Don't skimp on coverage to try and make the wiring (or lack thereof) easy. If he goes with a bunch of wifi versions initially, he'll at least be able to keep running them on 12v afterwards when he switches to wired data. Get a Dahua NVR to record everything if he's only using Dahua cameras or maybe a computer running
Blue Iris, particularly if he wants to mix and match brands. That's not recommended when using a standalone NVR.
Wifi security cams are kinda like an aluminum hammer. It LOOKS like it should work well, and the documentation says it's nice and light and fast, but it'll fall apart when you really start using it hard. One or two light jobs might be ok but don't count on it.
Also, with a lot of nanny/maid cams inside, I'd spend some extra time doing up a VPN for locking down camera access or he's liable to find his kids on porn sites.