We took on a fish tank while I was at uni, a lecturer was moving house and couldn't keep it.
At the time it had a large cichlid, a 6" silver dollar and a heap of goldfish and zebra fish!
We still have the silver dollar and large goldfish, the angel fish we got died recently, but we also have a leopard spotted plecostomus, a zebra fish, a tetra and a scissor tail.
When we moved from Hertfordshire to Aberdeenshire, the fish tank came with us, and the fish all survived (including the angel fish with her delicate fins!).
It was a 14 hour ordeal of a trip, but they were all packaged in individual bags with a small amount of water, an oxygen tablet (easily available on ebay), and the bags kept in polystyrene boxes. Reacclimatised at the other end by floating in the new water, gradually mixing it into the water in the bag before releasing.
Hope your son enjoys them, or bring them with you!