For me, the effort of digging out the turf far exceeds the effort of rotavating, raking and and any follow-up weeding. A rotavator will turn deeper than your spade/fork getting air into the soil, and you can use it to turn in manure too. I rotavated a weed-ridden allotment twice before planting it (with raking, it's very important to rake and collect up the weeds) and it was fine. New weeds are being delivered by air-mail on a daily basis anyway, but you can stay on top of them with a (dutch) hoe. You may also benefit by pulling out nettles and bindweed etc. before rotavating. With that all said, I own my rotavator (£120 well spent!) so if you are only hiring there may be better things for lifting grass, as Obelixx points out.
You will never be weed-free, whatever approach you use, and all approaches have their merits. But, don't expect that you can rotavate once and never see another weed (I swear some people have this expectation of rotavating).
Has your Dad said not to rotavate or not to use manure? I presume he said to mulch with manure rather than rotavate? That will certainly improve the soil, so if it's one or the other the manure may be your best bet. Mulching will slightly reduce the digging you have next spring but grass won't die off and fully decompose in 6 months with no air getting to it.
Good luck. This is a fine plot with great potential, you'll really enjoy harvesting your own produce.