Hi Sarah welcome to the forum.
Dont worry too much as long as you have all the documents needed plus good that you are working. I got my ilr last month waiting for less than a month.
You may include your sons docs ( birth cert, passports etc in your ilr application even the letter from his/her gp and clinic) I did the same with mine i included our 1 year old son's letters and docs.
Goodluck to your application
