Trocaderos always good. Especially when it's all buzzing and you can take in the atmosphere. Do something fun like the bumper cars. Or challenge her to a dance off on the dance machines. Lol.

Whatever you do, don't take her to madamme tussauds! I made that mistake recently. Its boring. Plus I made myself look like a right wally in the horror bit where all those live actors jump out at you!