My little one will also be 5 in a few weeks. Almost ever since I bought ipad 1 in 2010 he was using it a little bit (at first I was petrified he would break it, now we don't care). He has interactive books on it, magnet letters, musical instruments and all kinds of educational stuff (if I had to buy him all this as toys the house would be cluttered to the roof).
Today I showed him Star Walk first time and he loved it, asking me all kinds of questions about planets and stars (was whining a little when told his sign is Virgo and not Leo, in the end we agreed his will be Leo Minor and mama Leo Major because I'm bigger
) Anyway as was already said, I limit his time to 1 hour per day, I announce "now we will turn it off and go to the garden".
He is also unable to turn on tv remote and can't use computer mouse. But reading a real book before bed is compulsory. One thing I do NOT like is when he is colouring something on ipad with his finger. To hold a crayon is an entirely different skill and I do not encourage finger painting or writing for that matter.