7809 should do fine, provided the pedal runs off 9v which as far as i know most of them do. i.e. a single 9v battery. I dont think you will need a negative supply, unless a specific pedal does in which case it will either have two 9v battery's inside, or run off an AC supply.
I would build a beefy B+ supply ~12v with plenty of smoothing capacitance, then feed that into multiple 7809's in parallel for each output. If you look at the datasheet it will give you guidelines for local decoupling capacitor values, usually ~.1uf on the input and output pins, then add an output capacitor as a reservoir on each output.
http://www.diystompboxes.com/ is a great resource for pedal schematics so you should be able to find a few for commercial power supply box's. It would be worth studying a few to see the capacitance sizing and grounding layouts the real box's use. I suspect in this day and age most use tiny switching power supply's so you might have to go looking at older units from the 80's and 90's for linear supply's.
Also post pics when your done as i might build one too, building a few pedals has been on my todo list for a while...
P.S. center pin negative is an evil practice, why on earth would any manufacturer do that