Children born to an intercaste couple have choice to adopt the caste of father or mother as per their liking but that can be exercised only when they turn adult that is after the age of 21 years. Before that whatever caste their parents have written at the time of admission to the school becomes their caste and whatever benefits are allowed for that caste would be accrued to them naturally. You have not spelled out the exact reason behind your changing of your caste at this juncture as it appears a lot of inconvenient from the angle of changing your records at various places in the identity card, voter card, employee card, bank account and debit cards, Aadhar card, PAN card, educational testimonials, Passport, Ration card and many more where a change of name might be required subsequent to the caste change. So, I was just thinking whether it is worth to take so much of trouble in getting so many changes there just because you want to make a change in your caste followed by a change in your name if the caste is coming in it as a surname or middle name or whatever other way.
In case you have some personal or compelling reasons to do so then it is imperative that you would have to take the help of a lawyer in the matter because not only a legal affidavit would be required but also for name change the usual procedure of giving intimation in local newspaper and gazette notification would also be required. That is the procedure that has to be adopted for making your documents in order.
In our Indian culture after the marriage the girls drop their surname and adopt the husbands surname. This was alright earlier but now as women are also serving and have so many credentials many women are keeping their original surname to avoid the hassles of changing their name in so many places and also in educational credentials. You can take some inspiration in your case from there also if you feel it ok.
Thoughts exchanged is knowledge gained.