It is Sept. now, and IMPO it is best to get it in now.
Kids are back in school, nothing is going to change. By sending it in now, he/she can call the office in a few days after mailing it that they have a completed file. IF not, than they can mail any missing info.
Sending it in July is not something I would support, due to updating the file. Sending in mid Sept., once in school, and if they close 9/30 or 10/15, I would do it. If it is 10/30, I would wait a few more weeks, esp. if they take the Sept ACT/SAT to update scores.