Sometimes it can be a bit of a hit and miss affair. Some years its great and others it's a bit of a flop. I say this from a personal standpoint. I used to attend a lot of fish shows (back in the early eightys) and in my estimation you are 20 years too late, for back then there were no computers, playstations, Xboxes and the likes of to keep children in their bedrooms form dawn till dusk and an Open Fish Show was a family day out. But alas things move on and aquarist societies and their relative open shows are few and far between, many local aquarist societies have folded and the hobby as a whole lot worse off for it.
So that said, travelling from the Isle of Man specifically for that show, I personally would not bother but if you are in the area at that particular time then why not.
Sorry for rambling on
Regards
BigC