Polaroid film....if you can get in UK for ?20 a pack (of 20) you are doing well. No idea about outside of the UK.
And before you spend on the fuji, im 99.99999% sure it wont fit a 600 series polaroid, if its Instax then it wont, although it looks a similar size.
Fuji made film that fits in 100 series cameras. 600 series Polaroid cameras only take Polaroid 600 film.
..also agree Ed's kids are uber nice, then win my praise my generally being cool with me and not crying. I also dont ever recall them doing their business on me - which seems to be a common theme with friends children when they are babies and me.