The Texas Pinball Festival is a great show.  I've gone the last two years and had a blast each time.  Last year my youngest scored second in the youth pinball tourney.  The show has a good party feel to it as they bring in a DJ at night to get the crowd dancing. 

The three main shows I attend here in the US are the Expo, Allentown and Texas.  All three are quite different which makes it worth going to all three.  Expo is a "convention" type atmosphere, Allentown is a "flea market" type atmosphere where you can strike a good deal or two, Texas is as previously mentioned a "party" type atmosphere where the whole family can enjoy the show even if some of the members are not pinheads.