My favourite thing about staying in the Karoo is how big the skies are, how close to horizon the stars are visible! Coming from the city where light pollution hides so much, it's a treat. Twice I've been to Olive Grove, and both times was in Autumn, so I had lovely crisp weather. For night walking through the farm, you'll have a fresh and bracing experience, and you may well be woken by the merry sound of many sheep! (The lambs are adorable, I hope you'll get to see them). On my first visit I stayed in a self-catering guest chalet and this second time, in a guest room. Honestly, for a solo trip I think the guest room is the better choice, and even two people would fit comfortably, since there is one large bed and one small. Even if it's not self-catering technically, the guest room has a bar fridge, a kettle and a microwave, so if you plan well, you can easily cook for yourself. Because of the constraints of the room, you might find the fridge a bit loud at night (I simply switched mine off tho), as well as the extractor fan in the bathroom that's connected to the lights (but there's nothing so soothing as a shower in the dark).
I was at the farm to re-centre myself and work on my book, so I didn't avail myself of the catering facilities much. But the staff/family are really lovely, and when I needed a couple things they were more than happy to help. I would love to go back again on my own, highly recommended for a meditative retreat.
(Don't leave it to the last to fill up with petrol for your journey though, Beaufort West is quite a few KMs down the road, and the journey from the n1 down to the farm isn't brief either)