Heelp help helpneeded, wih kids?

im loooking after my friends 2 kiddies 4 afew hrs, aged 12 and 3, im not very good at finding things do with them and to be honest just cant be bothered , as my 2 sons are grown up and ive totally lost touch on what to do wih little ones now, scary stuff 2 me nowadays,, as got no grankids yet, any tips plesae from some experts, but no stupid answers