You can have reason installed on as many PC's as you want, you can also use Reason on as many PC's as you want, however you cannot use Reason on more than one computer, that being you can't have your licensed copy of reason running on more than one machine, you would have to purchase another license if you wanted to have more than one ignition key or to be able to run Reason on 2 computers or more at once.
That's why I said you can run it on as many as you want, you can always have demo modes setup on all the other computer, for your setup it doesn't sound like you really need more than one license (that is really only for people who run reason twice from two different location, eg. a studio and their home).
I recommend you just install reason on your home computers and laptop, keep your ignition key ready whenever you want to load up a project and that's pretty much all you need it for, whenever you're not at home you can take the ignition key with you and your mac book.
Remember that the demo versions only really limited in that you can't open any of your reason projects or export/bounce any of your project, which isn't really a big deal if you're starting a new track, and is not so much of a problem when it takes two seconds to plug in your ignition key if you did want to load up a project or export something. :)
Hope this helps.