what are you going to do for a vent?

what you want CAN be done, but depending on local codes, building type, and layout it could be very expensive or it could be just a few hundred dollars. for example, you may have to cut the slab and run teh drain over to teh main line. this may or may NOT be at the area you wish to tap the drain.

best advice i can give is to get a couple plumbers to come in and give you quotes on it.

Not only would you be limited by the vent, you would need to compute the existing DFU(drainage fixture unit) load on the laundry drain + the drains you intend to add to determine if the laundry drain is big enough to accept the load.