You can go for the main sector in chandigarh & mohali. Also strongly consider anything except 19+ sectors of Panchkula as that's a very well maintained area & extremely peaceful to live in.
Do not go for Kharar, Zirakpur, or basically any of the areas that are basically just flats like Sector 20 Panchkula if your parents are planning on owning a car and use it a bit as traffic is unbearable in those areas.
But if you want them to have some community with the society, then a flat might make some sense, but do consider the traffic even in that case as noise from traffic can get irritating.