I was curious about the laws and concerns of taking pictures in a public area, and I had a look at the UK laws, which states that there is no law against taking pictures of a public area of anyone including children. Of course, children you would need the parents’ consent, and if you were aggressive with the image taking, then it could be passed as harassment.
Moreover, although the coffee shop is privately owned, as long as you have consent from the manager then it is allowed, unless strictly permitted. Some people would not want their image taken, and may ask you to delete it after, but you can take an image of whatever you like as long as you have permission within a ‘private area’.
There is a document saying how on average, a Briton is caught on camera 300 times a day. I thought this was a really interesting to find out because of the amount of times an average person is actually being filmed, however when they see a person holding a camera, they tend to go camera shy(?!)
“General under the law of the United Kingdom one cannot prevent photography of private property from a public place, and in general the right to take photographs on private land upon which permission has been obtained is similarly unrestricted. However, landowners are permitted to impose any conditions they wish upon entry to a property, such as forbidding or restricting photography.
Photography of certain subject matter is restricted in the United Kingdom. In particular, the Protection of Children Act 1978 restricts making or possessing pornography of under-18s, or what looks like pornography of under-18s. However, the taking of photographs of children in public spaces is not illegal.”
Useful references: http://en.wikipedia.org/wiki/Photography_and_the_law#United_Kingdom