This year myself and DH and our 2 DC (10 and 8) went to North Wales for 2 weeks. We hired a self catering place (and mostly self catered). We went to the beach, did some shortish walks (up to 2-3 hours), visited all the CADW Castles and National Trust places within reach (have memberships) and also did some of the touristy things such as going down a slate mine, taking a steam train ride and visited Electric Mountain.
We all really liked the "having something to do each day" and it was all interesting enough both for the DC and for the adults in the family.
We'd like to have a similar sort of holiday next year but are struggling with finding a destination that has enough to provide interest for 2 weeks without breaking the bank.
DH fancies going abroad and has suggested the Black Forest, but I'm not sure there is enough to interest the DC for 2 weeks. I am clueless and open to all suggestions ...