With colo-rectal cancer, if there are no mets to a different organ and the lymph nodes are clear, it all depends on the tumour. They can tell if it has grown big enough to make connections with the blood stream and lymph system. If it has, your DFIL might be given oral chemo, just tablets to mop up any stray cells. This is debilitating, but you don't lose your hair and the side-effects aren't too much of a problem compared with other sorts of chemotherapy.
If the lymph nodes are affected, it's more likely to be a combination of drugs given by an infusion into a vein with more severe side-effects.
His surgeon will explain all this to him when he has his post-op appointment and his results have come back from the lab. Depending on the results, he might then refer him to an oncologist, who will decide which chemo will be best.
I'm stage 2, no mets and clear nodes, but I had oral chemo because of the nature of the tumour. It hadn't burst through the colon, but they found some cells in the soft tissue outside it. Now I'm being monitored with a schedule of colonoscopies and scans so that any new tumours are picked up early.
The best thing for him to do now is to try to focus on getting better from the surgery. I followed the low-residue diet they gave me and now can eat anything. Try to build up stamina with gentle walks. If he does have to have chemo, they'll probably wait a couple of months till he's strong enough.
It's a worrying time for you all, but the outcomes are quite positive for the earlier stages. Good luck!