yay thanks.. no idea really about the beach bit.. we are split between med and black sea boys are now old enough for us to be going to more interesting places so really looking forward to doing proper sightseeing!
Istanbul is a lovely city. I think you would be best to look for accomodation around Sultanahmet if you are going with children. There is so much to see there, The Blue Mosque, Haghia Sofia, Topkapi Palace, Dolmabahce Palace and the Grand Bazaar juyst for starters.
Food is amazing and very cheap if you avoid the obvious tourist places.
Where are you planning on going for the beach part?
I found Istanbul really family friendly but maybe not in the normal UK sense - places there didn't necessarily have all the baby paraphernalia (eg highchairs) but everyone seemed so friendly and accommodating to us and our toddler. we stayed in hotel levni and it suited us fine - not really geared around children but they had a travel cot and were friendly and not bothered by toddler running round. They had a Swimming pool too but it was freezing!