As per the title.

We’re down near Lands End in a couple of weeks. Would be good to get a couple of 2-3 hour loops from where we’re staying (although prepared to drive eg half an hour if it’s really worth it).

Gravel bike or MTB?

Is the coastal path do-able for an early (cheeky) bimble, or seriously frowned upon at all times?

(And also any suggestions for easy, quiet, child-friendly routes)

Cheers.

Bugger all off road really, patches here and there. I’d take the gravel bike iiwy and just have quiet rides down the lanes.
Some parts of the coastal path are OK but generally it’s rubbish for bikes, too many tiny wooden gates and grown in paths with nettles and ferns at this time of year.

https://www.cycleroutesuk.com/cycle-route/south-west/portreath-to-devoran-to-the-mineral-tramway-trail.html

probably your best bet for a family friendly route down that way. probably the shortest coast to coast as well…

we stay down in praa a couple of times of year at a family caravan and almost never take bikes.
walk, surf, swim, explore etc

You are a bit two far west for the good stuff, there are some routes from Helston but I don’t know them that well. Between Redruth and Truro there is Poldice which has lots of trails. You can link up Carn Brea, Carn Marth and Poldice.

EDIT: none of that is family friendly. Do the Portreath to Devoran C2C and you can duck off into unity woods or poldice on the way through.

There’s a bit of SWCP that’s Bridleway near The Lizard/Porthleven but otherwise it’s pretty-much all footpath with a million stiles/kissing gates to negotiate.

If you HAVE to be cheeky, go early to avoid walkists. And a lot of the SWCP is very narrow cliff-edge stuff, so maybe don’t go cheeky at night.

EDIT:
Yep, there’s a little Bridleway loop (a whopping 10+km ish) you can do in the Lizard Nature Reserve taking in the very lovely Kynance Cove.

Fat bike, wait for the tide to go out 🙂

Grogley woods is great if you want some enduro style riding. Check out trailforks, most of the tracks are on there!

grogley is a long way from lands end, doubly so this time of year.