With a 4 and 7 year old (mine are 6 and 3) look for a hotel that offers a LOT for children. A lot of Turkish resorts have kids clubs, playgrounds (some even have small fairground type rides) and various swimming pools with waterslides (though most operate twice daily for a couple of hours each time).
We went to Side (pronounced Cedar) in the Antalya region in May 2017. We stayed at a resort outside of the town and found the sister hotel (Otium Eco Club) perfect for young children. Very clean, quiet, smaller compared to others, fantastic covered playground and kids club, small fairground rides and 3 waterslides suitable for kids and adults. Pool depth was 1.5m at its deepest.
We've been to Marmaris too in the past and are booked to stay at the Club Turban at the end of July/beginning of August this year. Fantastic resort for children - various pools, 3 waterslides, kids playground, kids mini softplay, kids club, little fairground rides (payable), sandy/pebbly beach with gentle slopes into the sea AND it is on the road between Marmaris and Iclemer so it won't be rowdy. Perfect for families.
Turkey is a lot cheaper than the usual Spain, Portugal and Greece and you do get a lot for your money. Trips are a lot cheaper - we are doing a pirate boat trip (waterslide on the boat, restaurants, kids games and clubs) for £10 each (AI) and again a horseback riding trip for £8 each (kids are both free as classed as infants under the age of 6).
We found the Turkish people on the whole pleasant, chatty, jolly, polite and very helpful. My 2 year old went AWOL on the beach during a party last year at night and they had the ENTIRE entertainment crew as scouts on the beach leading to the sea so she wasn't gone long. It was one of those moments when she was joining in with the children during a party dance/game and it ended and as kids went in all directions to their parents and then parents walked forward to meet their kids, she simply got lost amongst the bodies! Contrary to what some people say about the Turks, they are very child orientated, family friendly and will do anything for you.
Be warned though about flights and transfers; flights are generally on the whole an evening flight arriving in Turkey anywhere between 9pm and midnight THEN a 2 hour transfer for most places.