Disney Sea is streets ahead of Disney Land, better rides and the evening entertainment where the dragon comes out of the water, well thats incredible.
If you have spare time, you can always walk up and down Fuji over two days - watch the sunrise at dawn from the top. Not sure if you can do it in late April though, can't remember if thats out of season.
Outside of Tokyo...Nara is a great place to visit for the heritage - both Hiroshima and Nagasaki are worth visiting for the A Bomb site memorials, very emotional.
I lived in Yotsuya, about 10 minutes walk from Chiyoda I think its called where the Imperial Palace is, an easy trip to see as it very central.
In terms of Pachinko, worth going to Akasaka near Yotsuya, loads of places there along with little alleyways and cool restaurants.
Oh and try go to Odaiba in the evening, you can get the tram over the Rainbow bridge and they have a cool shopping complex there, onsen, various electronic manufacturers buildings (more interesting than you would think!).