If you pay the extra to upgrade to the premium cabin the flight is fairly easy, you get so much more room to move around, free drinks and the ability to be able to stop and start the films which makes the time go very quickly. If you can't get premium seats you can still upgrade the entertainment so you can watch all of the films, for about a fiver, its well worth it.
Mossies shouldn't be a problem unless you intend being around stagnant water, the usual protection has always worked for me and the little blighters love me without it.
As for muggings, they can happen anywhere in the world if you're not sensible, don't wear flashy jewellery, secrete expensive camera's or take a disposable if you're really worried, don't wander off into isolated areas and you will be fine. My Mum and I in our mid 70's and 50's regularly holiday in the Caribbean on our own with no problems.
Good luck in changing his mind.