With the rank that you mentioned your son will get a variety of options according to the branch he will prefer or according to the college he prefers. You can check out the cutoff here

https://engineering.careers360.com/articles/jee-advanced-cutoff-for-iits/amp&ved=2ahUKEwj-3_jBmO3iAhUbQH0KHaV2AEAQFjABegQIBhAI&usg=AOvVaw0aewsFDhDrgwbrqB3QIbFv&ampcf=1

Good luck!

Hi! You have a very good rank in he advance. First of all congrats to you. Well, with this rank you will easily get IIT Kharagpur aerospace engineering. Other sections of IIT Kharagpur like biotechnology, chemical, and agriculture is also in your hand. Other IIT's which you will get are IIT Gandhinagar, IIT Jodhpur, IIT Patna. These are good IIT's where you will get other streams except CSE, ECE , civil and electrical. So hope you understand and best of luck to you.