Probably a good plan - it would be a real pain if one of your Aldi motors breaks and they've stopped selling them. Seems like the Argos ones are here to stay.

The other advantage of 12v is you can use more hobby RC ESCs, which tend to cap out at 3 or 4s. Note that the 12v motors will run quite safely, and a bit faster, on 4s, though 3s is fine. I've find two drill motors is more than powerful enough though, so it's probably a matter of whatever is easier to get hold of and fit in your machine.