DD is no longer in nappies but I always need to take along a snack, toy to entertain her, my carrier, jumpers for us all etc. so I wanted a decent sized bag when no. 2 came along. I was finding that trying to hold a baby and a toddler's hand, plus a bag and potentially shopping etc. almost impossible. And if you have a bag over your shoulder then when you reach down to hold your toddler's hand, it slips down and whacks them! Mybe that's just because I'm 6ft tall but it was driving my nuts. Ended up getting a biggish backpack from Kathmandu. (I'm sure other outdoorsy shops have similar too). It has heaps of different pockets and compartments so I can separate stuff, adjustable straps to I can lengthen them and hook it over the pram, and I've got my hands totally free to juggle little people. Wouldn't go back to a shoulder bag.