£1500 AUD according to XE
.com is worth £635.62 or 911.37 in funnymoney!
... so no, unless he increases his budget an EOS 300D, as cheap as it is, won't be on his shopping list.
Have you checked out dpreview.com
From memory, the S5000 is similar to the S602Z but with a 10x zoom (37-370mm in 35mm terms), the S7000 is very similar to the S602Z but with a 6Mp sensor but with only a 6x zoom (35-210mm in 35 mm terms). The Sony F717 has a 5Mp sensor but only a 5x zoom (38-190mm in 35mm terms).
All are fine cameras and very good at what they do but the real question you need ask yourself is what sort of aviation photography do you want to do the most of? You mention the long range aviation shots. If that's your target then I would advise you to save up a bit more, keep borrowing your grandpa's F717 for now (be nice to him!) and go for a proper SLR, and by proper I mean one with interchangeable lenses.
As Will mentioned, you're budget is quite close to EOS300D territory, but that will get you the body and if you're lucky the EF
-S 18-55mm lens. You will then need to budget for getting a bigger zoom lens to achieve the long range shots you appear to aspire to.
If however the long range shots are a nice to have but not the be all and end all, then the three cameras you've listed, plus the Olympus C-750UZ will probably all make you a very happy bunny.
I hope this has helped.
Flightlineimages DOT Com Photographer & Web Editor. RR Turbines Specialist