My dad had an ant's nest in his room as a kid. That is something I would love.
We set up web cams for the bairns (and us!) like 'squirrel cam', 'fox cam', 'wasp cam', 'mouse cam', 'bird cam' and it has given us hours of fun, as well as members of the family all over the place.
We have had lasers firing all over the place, and lots of other stuff.