I have taken my daughters to coin shows. They make out like little bandits. The older daughters don't collect anymore, but my youngest is a little money fiend and likes going because she gets lots of little freebies. One thing you should never ever take to a coin show is a wife. Send her to a shopping mall instead, that way she is NOT your minder.
Roundabouts not so bad. Is a lot of the roads I think got laid out by following the trail of a drunken moose
You could take him in a stroller but don't get too close to a table as kids can get grabby. As a retired cop I would also watch for stranger danger.