Covent Garden Market - Covent Garden has lots of kid-friendly eats in an informal setting, including fresh-baked cookies and ice cream, bakery and chocolate shop. May to October is an outdoor farmer's market with fresh fruits, breads, pastries, muffins, jams, evening night market.
The market is beautifully decorated for the Christmas season with large evergreen tree and silver stag statue, twinkling lights, holiday foods and sweets.
In summer, Covent Garden is chock full of street performers, jugglers, illusionists (we saw one guy suspended in mid air with no visible means of support), magic acts, people singing show tunes.
London Transport Museum - Underground trains were practically invented in London (the London Underground is over 150 years old!). The London Transport Museum is about forms of transportation, with an emphasis on London's own over the centuries.
The museum is filled with full-size double decker buses, horse drawn "omnibuses," electric railway cars, old-fashioned taxi cabs, steam locomotive, trolleybuses, bicycles, and galleries where kids can find out about how the subway was made.
Tip: This is one of the best London museums for toddlers - with hands on activities, wooden train set, play area where kids can pretend "Are we at the station yet?" as well as real double decker buses, horse drawn tram, electric railway car for kids to climb up and sit inside. Get the "Stamper Trail" card and punch each different stop.
Fun shops for kids are the London Transport Museum Shop, with model English double decker buses and trains, books and maps, a must for children who love things that go.
Somerset House Ice Rink - In winter, go ice skating on the rink in front of Somerset House. Rink is usually open November through January. Also at Somerset House, there are free arts workshops for kids on Saturdays, such as making collages or watercolors inspired by art from the Courtauld Gallery.