I got a real camera for my son at right about age 3.
NikonCoolPix
$50 during the Amazon CyberMonday Sales. ($200 camera)
7 years later? It's STILL going strong / taking great pictures (has taken thousands and thousands... some of which are framed on our walls).
I'd get them both the 'same' "real" camera... just in different colors, or with different cases. Your 5yo will be able to do more 'stuff' with it (messing with balance, etc.), but they're both solid cameras you'll be able to use and enjoy for years and years.
OptionB is something a lot of my friends have done. I got my son a smart phone ages and ages ago... but iPhones can still be used for music, pictures, GPS, 911, etc. with no calling plan. Typically, the prev. gen sells for a dollar.