Its a question to ask the local CFRC for the correct info. In my application process, I had move dates around to suit a work issue and it didn‘t cause any problems.
I‘ll assume you‘re referring to Reg force rather than Res. If its Res, then there may be other considerations.
Generally speaking, the application process (CFAT, medical, interview, job offer, fitness test, up to the date of BMQ) takes about 6 months. The waiting time may vary for different individuals, availability, skill sets, and MOCs.
The CFRC will ask you when you want to attend
the "CFAT/Medical/Interview" and the fitness test.
In most cases, you can chose the date. From my understanding, the CFAT result and the interview are valid for a year. The medical is valid for three months or at the discretion of the CFRC. If the medical expires, then you will be asked to see the CF Doctor again and spend about five minutes answering general questions. Its no big deal.
I‘m not clear what year you want to submit the application. Its OK to apply earlier in the year given that the process will take some time anyway. Just tell the CFRC that you want to finish out your football season and prefer to schedule a BMQ after August.
Take into consideration that MOC intakes for BMQ open and close periodically throughout the year and you may not be able to attend a BMQ directly after August or when you want. You may have to wait some time later. Most likely the CFRC will give you some idea of BMQ availability as August
gets nearer.
Good luck.