That PublicIP software looks pretty decent!
Looking at their diagram, you shouldn't need a wireless router; just a simple inexpensive access point like the Linksys WAP54G would do nicely provided you have the rest of the infrastructure they show in place. Most wireless products will cover 70m off the shelf if there are not too many walls, etc to penetrate, although you might need a slightly gruntier antenna for the best performance (about NZ$20-35 from
www.gowifi.co.nz for example).
If you need better range down the track, simply install extra access points (ideally of the same type) in repeater mode around the cottages.
One question I do have is how does your satellite connection work? The ones I have seen require a PCI card in a computer to operate. I would not recommend sharing the internet connection directly off your own personal computer. Ideally having it run through a separate router (either an off-the-shelf unit or a Linux box) would be the best way to go so you can limit access to any PCs you have from guests.