if you have a square speader bar, magnetic tape, that is, like a fridge magnet with adhesive on one side, might make a good way of sticking that strip to your spreader bar. You'll need to wrap the cable around the bar or similar or the weight of the wire will probably peel it off.

Should be a lovely light. Very little shadow etc. Be interesting to know how many amps?

What I have noticed with having a well lit tarp and reasonably spacious tarp is that our primary school age daughter likes to colour in etc under it - and it can turn out to be a bit of a kid magnet because they gravitate to the well lit area to play. That isn't always a good thing from my perspective, but she enjoys it, so I deal with it :-)