Filemaker Bento does not exist so scratch that one off your list. Bento itself has been discontinued for that matter.
Take a look at "synch tools" such as GoZync offered by SeedCode. It works with both FileMaker Pro and GO and does not require FileMaker server as I understand it.
Setting up each device as a client of FileMaker Server or Cloud would be a better option, but also much more expensive so the synch option is probably more likely to be in your budget range.