Jono, just because you would be jumping less than 6 metres while others jump nearly 7m should not stop you from joining, you'll catch up within a year or two and you'll be grinding with them side by side to break PB's. When I began sprinting (non competitively at the age of 14 I ran probably 12 seconds dead, 3 years later I'm running things like 12.8 or even 13 flat over the 100m after a long break. A year later and a bit later BOOM I'm grinding next to everyone who was already running 11's now attempting to be consistent with sub 11.5's.
If anything, it is much better to be with people who are better than you, it will always make you push hard... mainly because you feel shit and wish you were them, but in the end it creates incredible motivation and friendships.
You're excuse is like someone saying, 'I won't do gymnastics because there will be people performing maltese's and Victorians on rings while I'm struggling to land a handstand' - Everyone has to start from SOMEWHERE. Once you see something amazing in real life, you can aspire to it, trust me, youtube videos are not nearly as inspiring ![]()
Also, need not worry about your mile training interfering with your power output, ever heard of a decathlete? Ashton Eaton is someone you should (read: NEED) check out on youtube, absolute insane beast.
Either way, work hard, and the results will come regardless ![]()