Unfortunately, it seems that to run a wifi card in access point mode, you'll need a prism chipset: this page here lists the requirements.


That leaves use with two solutions:

First one:
-use ad hoc mode explained here
-start the Internet bluetooth connection explained here
-add a route command to link the two interfaces.

Second one:
-use a wireless access point to create the network (and I have one lying unused...)
-all wifi devices (including the tablet which will be used as a router connect to the wireless network and get their own i.p.
-the tablet is configured as the default router
-the tablet is also connected to the Internet via bluetooth
-add a route command on the tablet to link the two interfaces