It is pretty difficult to find the 126 cartridges that go into the instamatics. It has to be mail ordered and will be a little pricey for a mediocre quality picture.
The gnome pixie I think takes 120 film which can be purchased at most camera stores. It has the potential to give you great big negatives that can be fun. This is probably the most interesting of your cameras since the Gnome company is one of the very few Welsh cameras.
The coronet will be hard to get film for also it used F828 film... again it will be a custom mail order.
-----------------------------------------------
Your best camera is probably the Coronet with the Gnome being next on the list.
Take the cameras to a local camera shop they can show you how they work and tell you if they basically work or not. You can then clean the lens and run a roll of film through them. Unfortunately none of them are worth repairing you can pick up any of them for under $15.
http://www.filmforclassics.com has some funny films and developing.
http://www.frugalphotographer.com/cat126.htm shows how to get and process 126 film.