I would layer over a much larger area than you plan to use as a garden
if it is a big patch of ivy. I think you'd want at LEAST a 3' border
where there is no ivy or any other plants, otherwise it will just come
right back into the garden.
I'd also use wet cardboard instead of wet newspapers for the bottom layer.
I'm off -- out of town for the weekend, happy gardening!
Eliza