We love Mark Warner. We've been to both the other Greek resorts.
This one looks gorgeous and we'd love to go! I mostly want to laze by the pool, interspersed with aerobics classes. DH wants to sail, and the DDs want to stay in the pool until they're prunes.
For childcare, there is no other company doing such a good job for European holidays. I love that the childcare staff are trained and registered in the UK. The activities are always well planned and varied. I love seeing my kids' groups wander through the resort on the way to sailing or sailboarding or swimming. I feel constantly reassured about their safety - ratios are great and the staff are so engaged. They go every morning so DH and I get a break then we all have time together in the afternoon. But you never feel far away as you see them pottering about and can go and see them anytime. The end of week performance is very sweet - I've heard them practicing their songs during the week on the way to activities. And the cost of childcare is included!
Evenings are great, too. High tea is a great idea - my two are often shattered after a full day of activities and swimming so an early supper is perfect. And one or two nights they go to the listening service - a movie then their own little beds til we collect them. They're safe, and entertained, and we can have a leisurely dinner together. We've also used the babysittering service so we can head out for dinner in the local town - absolutely no issues and reasonable rates.
We've seen the older children, too, and will definitely consider Mark Warner when ours are teens - they seem to get a great deal of independence in a very secure setting.
Food is great - always a super buffet that's very fresh and local. Definitely doesn't feel beige or catering for the pizza-and-chips brigade. The wine at meal times is decent quality, too. Lots of snacks and drinks available throughout the day as well. There's always somewhere pretty for a sundowner as well 
DH and I have been able to sail together, and take the kids out on the boats as well. Tennis too, which DD1 loves. DH has also been on scuba tours arranged from the resort. Lots of activities to do - the fitness programme is a good way to keep up the good work done before summer to lose weight. Really cheery instructors and a range of levels and styles to choose from. We've also hired bikes to tour locally which is a great way to get around. The adults-only pool is also a lovely touch - I love my own kids but sometimes want to swim without an inflatable smacking me in the face. I've also never once had to fight over a sun lounger - plenty of umbrellas by the pool and on the beach as well.
Airport transfers are incredibly well organised - the team meeting arrivals are a MACHINE - and check-in is a breeze. Lovely clean rooms, well suited for families. All staff are very helpful and knowledgeable; the wait staff and cleaning teams are always very kind to the children. The resorts are a good size to get around - everything is easy to access but you don't have the disco or pool right outside your room. The welcome evening and quizzes and discos are a great way to get to know some other families.
Like I said, we really love Mark Warner 