Need new backpack/day pack

[Pixieshouse]

I have a baggalinni messenger sling back bag that I have been using for years. But one shoulder seems to take the strain after a few days of walking around Disneyland with the kids.

Do you have a favorite backpack or bag that is good for your back, can tote water and snacks and the ocasional change of clothes (potty training right now).

I like the weight of the baggalinni, the fabric is nice and I don't seem to get to terribly hot with it. So something around that line would be good I guess.

Thanks!