Make sure your cage is large enough for three (
Guinea Pig Cages, Your Cavy At Home ). Then, I'd totally clean out the cage, wiped fresh with vinegar and water, fresh bedding, even clean the houses and food dishes. Then rearrange it all, and put the three in there at the same time.
The dynamics of the mom/daugher pair will probably change.
Even though your male will be neutered, there will still be rumblestrutting, chasing, and mounting going on.
Oh, and make sure you wait three weeks after the neuter before you do any of this!