Hi S.,
London is a great city. You will have lots of fun. Are you familiar with the tube system?
If stonehenge is your priority, there are coach tours from London for a day or so and cover a few other places along as well. Last time I was there, there were a few from the Victoria coach station. Its easy to find the information once you land, but its better to make a plan ahead. For local commute, we use something called Oyster Card, which is quiet convenient.
Within London, it would be prudent to group the places you visit and allocate a day for the group. For example, a visit to Knightsbridge will help you cover places like Harrods, Museum of Natural History, Science museum, V&A museum, all in the same go. These places are so huge, it would take a few visits to appreciate them, however, on a vacation, this is the best we could plan.
Another example would be something like Greenwich ( where the meridian line is). Cutty Sark is somewhere nearby along the way.
Not sure if anybody has mentioned about the London Eye- this gives the fantastic view of the city.
Kew gardens is another great place to visit.
I think it would be a great idea to think/discuss what your interests are ( like science, architecture, arts, gardens, zoos, history, or just plain fun) and identify places. London alone has everything to offer.
Oxford Street is a busy shopping street and closeby is Hamlyns, supposed to be the largest toy shop.
If you have plans to explore a bit more, one of the places worth visiting is the north east ( thats where we stayed before moving to scotland). North east has fantastic places like Bamburgh Castle, Alnwick Castle ( where the Harry Potter scenes were filmed), Durham Cathedral, Lindesfarne castle etc.
Scotland is a land of beauty. The Loch Ness in Inverness is a place of great beauty.
Katie,
Thats a great list.
Other Mamas,
Great advice.
Thanks