The bottom line answer is no on the wire. You can't run low voltage in the same conduit as high voltage per the National Electric Code (NEC). If you have a short in the high voltage side, then it comes back and hits you equipment, which will promptly be fried... Then, to make things even more fun, starts a fire because nothing in your equipment was designed for 120v over the speaker output, so you burn up (let's be nice) half your home... Then there is an investigation and it is tracked to a violation of the NEC. Insurance now denies your claim.
Not really something you even want to consider.
Direct burial is definitely the way to go and there are many wires available for this and they can be run a LONG way without any issues at all. Wireless I have not heard of anything that good. But, outdoors... and you apparently have 120v available to you at that location... so maybe something could be figured out.