In reply to funkyvin1:
Well if you had another adult to belay, you could take him/her up one of the classic easy climbs at Wintour's Leap, they are very easy but that would be quite an adventure! Failing that a circular walk round the Leap taking in the easy descent (preferably as an ascent) is a good scramble requiring care, like any scramble, with a terrific outlook.
Further up the Wye is beautiful - as kids we used to swim in it, and I probably will again, not sure how recommended that is nowadays though. Just choose a riverside walk and pick your spot.
The real honeypot of the Wye valley is Symonds Yat, there's canoeing, caves to explore and all sorts there. There's even a pinnacle to climb - again you could get an adult to belay you, they wouldn't have to climb it themselves, and you could bring your child up then abseil off (with a safety rope, of course.)