Traveling to Hamburg in April

Me and my 14 yr old son are traveling to Hamburg in April. We both play foosball. He won entry to the World Cup being held at Kampnagel. He is part of the US Jr team, and I am the captain.

Well be arriving on the 5th. So, we have 5 days to visit before the tournament starts. We plan on making a trip to Berlin for a few days.

I am coming here to see from people who live there, or may have spent some time there, that can let me know some things to possibly do. Also, make let me know what areas I should avoid.

As of now, I have a room close to the airport Best Western Amedia. But, it's not quite as close to Kampnagel as I would like, but the rooms are getting scarce. I have also looked at Heikotel City Nord, it's closer, and not much more.

What are some acceptable areas to look into staying in Berlin? We want to go to museum island, and possibly do the Berlin Dungeon tour(?)

Any other ideas we have can be said if needed, and I am open to all ideas anyways.

thanks

JJ