I would highly recommend Parco delle Piscine as a holiday destination for families. We have two children aged 9y and 6y and were there with another family with children aged 7y and 5y.
The village of Sarteano itself is lovely and relatively unspoilt. There is easy access to local bread shops (50m from the edge of the campsite) pasta shops and gelateria. There are lots of great small and reasonably priced local restaurants serving typical Tuscan food. (We particularly liked Locanda Dei Tintori). There is an interesting historic castle which is worth climbing and exploring. The streets appear relatively unchanged over centuries and there is a rich local history particularly around the summer jousting competition between the 5 local contradas (neighbourhoods).
One real bonus on the campsite is that the pools are not chlorinated as they are served by a natural spring - great for avoiding stinging eyes and fussing about goggles. There are two waterslides in the main pool.
The Eurocamp courier Phil was extremely friendly and helpful and keen to ensure we had a great holiday. He could not have been more friendly and welcoming. He went out of his way to engage with us and our children Including setting up a telescope on our last night so we could see the moon and Saturn and pointing out other features of astronomical interest.
The campsite is also served by Wintours holiday club. We did not regularly use this facility other than for the daily Happy Disco which the kids loved.
There was lots of interesting wildlife for the children to find including lizards, toads, beetles, damsel flies and even the elusive hoopoe birds (although an early start is required to see them).
The lack of a campsite shop is not a problem since the village is so accessible.
There are good sports facilities on site with plenty of open green space for ball sports as well as table tennis tables, tennis courts, a basketball court and a shady and large children's playground.
All the pitches are large and well shaded. The tent and caravan area is quiet and peaceful and separate from the pool and bar area.
The communal shower blocks are very clean - I was never there without encountering a cleaning lady.
There is a short, easy and picturesque drive of 10 minutes to a large supermarket but most of what you might need is available by walking into the village.
Sarteano is well placed for day trips to either Rome, Siena or Florence and Montepulciano is also nearby.
I would not recommend the site for families with very small/non-swimmer children as there are no really shallow pool areas but other than this I think it would suit most families with school aged children.
We rented a car from Rome airport and drove and this was easier and more direct than we had expected, taking about 2 hours.
So in summary:
Pros:
Great pools
Great food
Great location
Great weather
Cons:
No shallow/ graded depth pool
No central campsite social hub as everyone tends to go into the village

We had a week here followed by a week at Camping Valle Gaia. This was a really nice site with beautiful pools (especially the site exclusive one), great big grassy areas for the kids to play in and the high point was being able to stroll in to town and sample the local restaurants in this really pretty town. We stayed with Eurocamp and the accommodation was modern and clean and the Reps were all friendly and helpful.

Down points: pools could get busy especially with locals. The pool for site use only didn't open till 1 July and so we only got to use it for part of our holiday. It would be good if it opened a bit earlier in the season as the other pools were very busy (but never too busy to get loungers). It was beautiful though and more relaxing than the other pools and lovely views up to the town. Think a few locals may have been using it too although meant to be for people staying on the site only?

Some of the bar staff seemed quite new and service was a bit erratic with a few watery cappuccinos for breakfast towards the end of the week and some variations in prices charged!

Only ate at on site restaurant for lunch and weren't tempted to go back. Strange wee place with no atmosphere. It was quiet but service wasn't great and we had heard similar stories from others. The food was good but I would suggest a short stroll in to town for a better experience.

Overall, we can highly recommend this site and hope to be back soon. We are regulars at Valle Gaia and it rates similarly to it - pros are you can walk in to town from this site and more flat, grassy areas for kids to play than Valle Gaia. At Valle Gaia the on site bars and restaurant / pizzeria are much better and it is also a shorter journey from the airport but you do need a car to go anywhere. We liked having a week at each site to enjoy the different locations and to allow us to visit the gorgeous areas around these sites of which there are no shortage. Can highly recommend.