Zeenith, we live out of Tagaytay some way along the ridge road in the Nasugbu direction and have done for 16 years. So don't have any detailed knowledge of all the subdivisions which have sprung up in Tagaytay in the years since we first started looking for property.
Tagaytay has no real one center...but there are two main roads to Manila coming in, the Santa Rosa road and the Aguinaldo Highway. Most buses to Manila use the latter, so as your child needs to go to QC occasionally it would be best for you to find a place, not necessarily right there near the Olivarez area, but not too difficult to travel to.
But public transport along the Ridge Road is good, except at weekends and holidays
Concentrate on subdivisions on the North side of the ridge road. Going East towards Picnic Grove there is Southridge, a long established subdivision. But other newer ones have sprung up along that road. Then there are some subdivisions just a short way down the Santa Rosa road.
Going in the other direction from the Rotunda towards Nasugbu look for Magallanes Shopping Center, take Memory Lane and there are some subdivisions down that long road.
Carrying on the Nasugbu road take a right and there are some subdivisions on the way to the Mahogany Market, (by the way a long established private school near there), including some off the Amadeo Road, which is an alternative way to Manila, recently upgraded. Metrogate Estates has a large subdivision in that area.
Carrying on along the Ridge Road towards Nasugbu and you come to another commercial center in Tagaytay, Mendez Crossing. MC is a bit rough and ready but the road to Mendez has some new small subdivisions, and there are a lot of subdivisions as you follow the road to Nasugbu...one is Sotogrande, it's within walking distance of the Savemore and buses at Mendez Crossing. Don't think you should go too much further... the limit of Tagaytay is about 3 km further on at the Zoo.
My wife and I have our home in a gated subdivision just outside Tagaytay on Tagaytay - Mendez road.
Were not retired and living there full time yet so I can't really offer any thoughts on other locations, as we can only spend 3 weeks a year there, but I'd be happy to answer any specific questions you have about the one we (will eventually) live in.