Enoshima aquarium or Osaka aquarium

During my travelling to Japan for 16 days this March, I with my 2 sons (9 and 12 year) plan to visit many places including Kamakura and Osaka.We wish to visit 1 of the 2 aquarium.Which one should we choose?
One more question please. Is there heater in night train?

i have been to the aquarium in osaka and enjoyed it - they have a huge tank with amongst other things 2 whale sharks (or at least they did 10 years ago). i don't know the enoshima aquarium. I have also been to aquariums around tokyo - kasai rinkai koen, kawasaki (i think) and in an office building in shinagawa. osaka was the best aquarium but kawasaki and shinagawa had performances.

as for the night train, i have yet to find a train that wasn't overheated but i'm not sure that the kiddiwinks could put up with an all night train ride.

sorry, i misread your post a little. i guess the tokyo stuff is irrelevant.

Thank you, Joseph.
Sorry, I don't understand your answer about heater in night train.

Is there heater in night train?

Virtually all trains in Japan, including night trains are air conditioned.

I am from Fujisawa, where Enoshima is located. Enoshima aquarium is really cool since it's new, they just renovated the building, and it is Right next to the beach - and the enoshima (isnland). Enoshima aquarium has the biggest? jellyfish exhibition and I like it a lot.

i think all trains are heated. my point was that as it is winter everone dresses warmly so the trains are in fact too warm.

I was in Japan last summer, a family with boys 12,10 and 7. We all really enjoyed the experience of the night train from Osaka to Tokyo. I thought the temperature was just right (there must have been some air conditioning). I didn't get as much sleep as I would have liked, but the boys slept fine. It would probably have been cheaper to get a cheap hotel room (you have to pay for the beds on the night train even if you have a rail pass).
We thought the Acquarium at Osaka was fantasic, there was the whale shark (just one) and some fantastic big crabs I hadn't seen before. It was by far the biggest aquarium we had ever been to - you keep spiralling downwards around an enormous tank with periferal exhibits too, but it was the only one we visited in Japan. It was so good it would have been nice to visit others...