Hi Pete, I have half the answer to your question.
http://www.amazon.co.uk/Neet%C2%AE-D...5614857&sr=1-3
This will convert the digital output from your TV to rca stereo. Since I don't know which type of input the 3.5mm jacks require, I can't help with that. If they are just 3 full range stereo inputs then simple splitters may work. Do you have any further info on the 5.1 kit?