My wife is not real good on the computer and all she really needs it for is her itunes, storing pictures and face Book and to back up her Iphone. She needs to be able to easily access her pics back ups etc. What one would be best for her?
She can use the iPad to make purchases and rentals via iTunes. If she enables photo stream on the iPad, that is sorta like a backup, but I HIGHLY recommend that she use some sort of external or cloud storage for safe keeping, whether you opt to get her the iPad or the MacBook. As for Facebook, she can access it via the iPad's browser or via the iOS Facebook app.
She needs to be able to easily access her pics back ups etc. What one would be best for her?
If she uses an external storage drive or a cloud service then having access to her backup photos etcetera is fairly easy. If you're referring to the backup of her iPhone as a whole, neither device will allow her to pick and choose what to restore. Anyway, from what I gather, she should be okay with an iPad.