ale yeast ferments warm enough it shouldn't need a diacetyl rest.
in fact, i've only heard of a diacetyl rest when speaking of lagers, as the cooler fermenting temps prevents the yeast from cleaning up the diacetyl, so you bring it up to the 60's for a few days, then go to secondary and back to cold lagering/conditioning.
But you're absolutely right about Wyeast's recommendation for this yeast. Fermentation temp is 64-74F... 70F should be enough for a rest. I'd probably give it a few extra days in primary for the rest, then rack to secondary.
So, after 3 days of consistent FG readings, I think your plan of 3 more days for a rest is a good plan.
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10