Two ideas (using tricks) for your situation.
1. Send to all Reaper laptops tempo via osc events, so they should have always same tempo in bpm.
2. Now they could be still out of sync, for this you might try another second trick, something like stopping music and starting immediately again, just for resync purposes, you could trigger this command in musically fitting moments, like breaks so listeners think this is part of the music.
I hope these help you eventually, at least you have something more to try.
Trick 1 I am using myself, I am changing tempo of Reaper via osc (with the help of oscii-bot), then you can load a midi-clock vst* which can go to all your other hardware. So slaving the hardware should be not the problem at all. Only how to sync the other Reaper laptops, for that you could try trick number 2. Good luck.
*
http://antonsavov.net/cms/projects/as_xc3.html