Celine673:

Teamlab have two exhibits, one in Odaiba, and one in Toyosu. They are both quick access from Conrad and far from Hilton.
I would stay in the Conrad, do Odaiba (that Teamlab exhibit has more interactive things you can do with kids), walk around the Hamarikyu gardens if you like, and you can go into Shinbashi/Ginza for dinner/shopping.
Shinjuku is just hordes of people and I don't recommend bringing two kids into the hordes of salarymen and commuters at the train station. You only have one night so you won't be able to do much.
I used to be gold - free breakfast in the restaurant, no lounge access at Conrad, but having said that I've never received an upgrade at Conrad despite staying 6 times as diamond.
Hope that helps!