Im not 100% sure so forgive me if poss but I would think having a 25a fuse would be better as your circuit and relay would be protected more imo? .
Personally though i would wire them seperately on 2 relays but aslong as the current drawn is adequete i cant see a problem unless the two pumps draw too much for 30A.
Also presuming the live feed to the pumps are direct from the battery through the relay which is 'live' via your switched earth from the ECU.
Earthing the pumps direct the the earth terminal is a prefered method preventing less resistance helping the pump voltages stay good.