My question is whether it is advisable to take children of this age

As far as taking kids this age on a sailing trip, it depends on the kids and
the parents. My wife and I spent 10 yrs cruising central and south American and
the daughter brought her two sons down for 2 months every summer. The started
at 3 and 5 yrs of age and they had a ball. We had no problems of any type.