No, they each have to be individually selectable by the PCI controller. There are mini-pci breakout boards, but they are difficult to find and I have no idea if the chips they use (they have to be active - they make the card look like a complete sub-pci bus) are properly supported by Linux.
There are boards supported by OpenWrt with multiple (mini)-PCI slots. Using the x86 target you could try mini-ITX boards and the Soekris boards, and then moving to other architectures the Routerboard 532 supports two mini-PCI cards, as does the 112 and the 153 and 133 both support 3 mini-PCI cards. But the support the the RB1xx series is still a bit experimental - there is at least one patch not (as far as I know) in svn yet which is needed for PCI support on the RB1xx series.