I'd be very surprised if your wife noticed adverse effects while a Windows backup is running. My wife plays games (LOTRO, gods help us) and she can't tell when the backup kicks in. Edit2 - her machine is wireless & she's not clueless
Contrary to popular opinion Windows backup does a decent job & will maintain daily/weekly/monthly backups for years. The initial backup will take a while but after that its a couple of GB/day for most users.
If you have multiple machines then Windows again does a decent job - provided there's a Windows server** in there - as it'll also provide de-duping* facilities.
tl;dr have a play with Windows built in backup first - you'll probably find it'll do what you want. Edit - backing up & restoring 64-bit versions of Windows from 32-bit versions of the OS server is do-able as well - I've restored the kids machines several times, usb stick in, boot up, enter backup password, walk away for a couple of hours (depends on network speed), remove usb stick, reboot & job done.
*no point in storing 5 copies of the same version operating system file
**Windows Home Server was decent, dunno about now as I still run WHS2008 (which is Windows 2003 server heavily scripted). Runs forever IME, year+ times between reboots are normal, although I dread the updates then