These people are not lazy unfit modern people. Their primary transport is walking in an age when you walked or stayed home. This means that their baseline of physical fitness is higher than ours.
Their required gear is considerably more basic than ours. We'd carry changes of clothes, cooker and fuel, tent, sleeping bag etc. etc. that these people wouldn't even think of. Sleep under a tree with maybe a bedroll, (folding) hide pot for cooking, firelighting equipment, bow for hunting.
Terrain is against them, no modern or Roman roads to speak of, uneven ground, forests can be surprisingly open at ground level, or totally impenetrable due to undergrowth. Occasional forest fires and browsing animals will keep this clear, depends on your environment. If it's clear then an open forest can be very easy soft ground to walk for miles at a time.
Modern experience (personal), we used to do 50miles in 4 days in wild country carrying full kit (1/3 body weight) while being experienced but not especially fit city teenagers. We did this in the knowledge that we could have covered that distance much faster without load, easily two days even on that terrain.
Hostiles are possibly irrelevant. You're talking about an age with a much lower population density, once you're a day's walk from a town you're unlikely to see anyone unless you're on a direct route to the next town and even then merchants and highwaymen only. People didn't travel much, soldiers would be on the roads not in the back country, highwaymen would be on the roads to find targets, no point being in the back country. The adventures will come at the river, the rest is just a lot of walking.
If they want to make a route march of it and get lucky hunting: 9 days or fewer.
Steady walking with a little time to gather food: 12-15 days.
This is actually the biggest problem, it could add several days to find a crossing. They probably can't swim, there probably isn't a ford, there won't be a boat unless they find a town which I get the feeling they're avoiding. They'll have to follow the river a considerable distance to find a suitable place to cross, the first crossing inland from the sea will almost certainly have a town or village. Depending on avoidance of others/country/terrain/river width/speed/etc. add 1-6 days just to cross the river.
As an example, Harwich and Felixstowe* are port towns on the English East coast. They're a few hundred meters apart. To travel from one to the other without a boat is over 30miles, even using the new Orwell bridge. Without a crossing a river is an impassible barrier.
n.b. For a modern hiker on a known trail: The Pennine Way, 268 miles, can be done in around 3 weeks with no particular hurry, carrying full kit.
*Arbitrarily selected because I know the towns not for any other particular reason, I'm sure there are equivalents requiring far longer detours.