[OOC: Lords of Men (pg 102) has a little bit on the military forces that can be raised by a noble. That suggests for a Poor or Average Noble in a strongly feudal area they can raise 5 Light Cavalry, 10 Infantry/Archers and 10 Levies, but that the Levies are only available whilst on home ground.
The military forces locally is going to be a lot more weighted towards Light Cavalry. Given that, 20 Light Cavalry seems not ridiculous, but at the high end of sensible. Maybe reduce to 15, i.e. 3 Combat Groups? As you point out, there's also an issue with having them for an extended period of time (Nobles have their levies which are only available on home grounds) - maybe a significant proportion of them need to leave once the immediate problem in the local-ish area is dealt with?]
Gregorius's dress doesn't advertise his status, although those watching the group dynamics for a time might identify him as a source of decision making. He's wearing his suit of partial leather scale mail, and has his axe hanging from his belt along with a bag of slingstones [remind me when I inevitably forget that the resulting encumbrance gives him -2 to relevant rolls, including casting totals]. Several more bags of slingstones are loaded into his saddlebags (along with supplies). He's also brought his stock of vis with him [4 Mentem, 6 Rego], although is hoping very hard that he doesn't end up using it.
Gregorius nods. "Probably more travelling today than fighting, but we'll see."
He doen't push the warband hard, wanting to avoid arriving tired to battle. He sends a couple of pairs of mounted scouts ahead of the main warband - a lot closer in than Fray is, and intended to warn of ambushes and suchlike rather than to actively look for the Amazons. He also pays attention to his Premonitions, although he's acutely aware that they're significantly weaker away from the aura of the covenant [Per 3 + Pre 3 + Aura + die].