hi pax,
The two devices I have suggested are LOCMOS, which should put a minimal load on your MCU outputs.
If you find the total 'bus' load is too high for your MCU, you can install bus drivers on the MCU pcb.
At this time I cannot find the part number for the 'high side' rail switcher device, its a 5pin tab device.
Perhaps someone else might recall the PtNo:
Eric
EDIT:
The LTC1981 high side switch, can be purchased in single or double types..
A MIC2514 would suit your application.