We had a fabulous holiday here. 2 adults and 2 teenagers. The villa was spotlessly clean and the pool was lovely. Maid service every day and the rep also contacted us almost every day, often bringing cakes, to ensure we had everything we wanted. The villa was really peaceful and quiet, very relaxing. The wifi was adequate for all our needs.
Kolymbia is a small family resort and we didn't spend much time there, but it was a 10 minute walk, 15minutes to the beach, if you wanted. We stayed by the pool! It is well located for visiting other parts of the island, being halfway between Rhodes and Lindos, plus close to one of the roads crossing the island. I would say a car is essential.
I wouldn't recommend it for families with very young children as there are marble floors, split level rooms, and the pool is directly off the patio, with no barrier to stop small children accessing it. Once your children are safe near water it is a fabulous holiday location.