We've been on a couple of walking holidays (& one cycling holiday) with DC though we went on plenty pre children.
First time we only had DD and she 2½ years old at the time. We went to Jordan and had a great time. The other children ranged from 2-10 years old but it was only a easy walking trip.
Our second trip was to Morocco. DD was then 6 and DS was 3. Again a great trip with mule support for when the kids got tired. Both the trip were with Families Worldwide.
We've also been on a Freedom Treks cycling holiday in Holland. It was short cycles every day plus something interesting for the kids, either a park, farm or other attraction. We had a floating hotel in the shape of a large barge so everything was transported along with us and all meals were included too.
The group on that trip was a little different in that there were families from Spain, Italy, France & Germany as well as the UK. But the kids got on despite the language barrier and we had a great time.
I've just got back from my holiday, and it was fab. The week cost £700 each for dh and myself, £350 for dd1, and dd2 was free because she is under 11.
Some people may say that is very £££ but there were almost no extras (just drinks, and our bar bill was £70 for all of us for the week). All transport to and from the walks were included, and there were plenty of guides and play leaders, all giving their expertise unpaid. The dc loved filling their lunch bags with a mixture of healthy and chocolate, cake and crisps not so healthy snacks. When we got back from the activities they jumped in the pool, and after dinner player out with the other children until dark.
It's rare for us to have change from £2000 for a family UK hotel break (we had 2 rooms, and not sharing with dc was a bonus). Plus we didn't have to drive around to expensive visitor attractions. I would fully recommend this company, and love the fact that 11-17 year olds are half price. Too many other holiday companies only give reductions for very young dc.
A friend of mine has just done one with them. She said it was great, the whole family really enjoyed it. It does sound like an 'all join in' type experience though, down to sing a longs on the bus etc. I thought it sounded great but DH was horrified!
We are looking at going to the Isle of Wight with HF holidays.
My dh is a walker, but I'm not particularly fit. However, I think I would be fine with the shorter family walks. Dh could sometimes join us, and other times do the challenging walks. Dd1 is 12, and likes walking, but can be shy. Dd2 is 9, and can be lazy, but is up for this because she thinks it sounds exciting. It's not a holiday for being secluded, you eat meals with other families etc, and is totally different to anything that we have done before.