The bus from Airport to City Centre is no hassle, it drops you right in the city at a sort of central bus stop area where you can get a bus onto Anfield (which is only a short distance), there were a number of transport officials working at this bus stop area who will help you get the right ticket and bus!
Also i'm sure any 4yr old would love a trip on this, it was very funny and unusual! Again its close to the city centre at the Albert Dock, I would highly recommend this for a bit of fun! [broken link removed]