We're heading to Beeches Farm campsite above Tintern Abbey and a stone's throw from Offa's Dyke (an earthwork built by King Offa in 750AD to mark the border between Mercia and Powys - i.e. England and Wales).
For the climbers there is Wintour's Leap where you'll find panoramic views across the valley and the river. Shorn cliff has a selection of single pitch routes, with pocketed limestone and good tree anchors. Symonds Yat (a little further afield - about 35mins drive) is famous for the river rapids and a free standing pinnacle to ascend. Wyndcliff has both sport climbing and trad. There's also well-sheltered quarry climbing at Tintern Quarry.
For the walkers a couple of obvious options are to walk south, cross the river in Chepstow and come back up the other side. Or walk north cross the river at Bigsweir and come back down the other side. But there is plenty else to do, just browse OL14.
For cultural types; Tintern Abbey, Chepstow Castle and Monmouth Castle.