Eyelid Surgery OK if Prone to Keloids?

True keloids of the eyelid are extremely rare. However, it is worth bringing your concerns to the attention of your surgeon. The surgeon will assess scars on your body and your medical history to determine if you have a true problem with how you heal your scars.
Also I will advise extreme caution in picking a surgeon to address your congenital ptosis in India. You want to find someone who has fellowship training specifically in eyelid plastic surgery or pediatric ophthalmology and a residency training in ophthalmology. They should have a reputation in congenital ptosis surgery.
A general plastic surgeon, general ophthalmologist, or facial plastic surgeon are generally not going to possess the skills to help you. You might look up Miland Naik in Hyderbad, India. If it is too far to see him, his office might have a referral closer to home for you.

Typically, this operation leaves hardly noticeable scars, however if you develop keloids elsewhere then it is theoretically possible to develop them anywhere. Depending on how severe your degree of levator ptosis is you may need to stop and reconsider the operation.
Many times, patients will have their levator ptosis fixed just to get insurance to cover their blepharoplasty. In your case this would be a very bad idea for obvious reasons. If your levator descent is such that you are having difficulty seeing and there is a clear medical indication for it then there comes a point where you and your plastic surgeon will have to consider playing the odds. Many patients think they have a keloid and it's a hypertrophic scar so that also needs to be looked at. Unfortunately, you are an interesting case.
Best Wishes.