my son has score 186 marks in advance 2018 , will he get iiitd?

First of all considering this year's paper's difficulty he has surely done a good job and will get a good all India rank. In response to your query I would say that if he is from general category then he might get the iiitd but he may have to struggle through the streams available. Most sought for courses like computer science had opening and closing ranks of 3 and 103 respectively. Electrical engineering had 226 and 410 respectively. And then the less popular courses like textile technology had 2958 and 4807 respectively.
All the ranks mentioned above are for general category and the comparison for courses is solely based upon student's rating and not my opinions.
So I wish him all the luck.

It depends on the rank which he gets. At 186, your son might get a rank between 3k - 6k. He can the biotechnology and textile streams in iit Delhi. Best of luck.