Just a note of caution on the Neilson option, take what they say about excellent MTB resorts with a large pinch of salt.
We went to Vassiliki for a week in September about 4 years ago, based on the rave reviews of the MTBing. The missus and I went out with the guide on day one and did a few good hours with him. She then went back and I did a further couple of loops which were ok. When I asked him what was next he said we’d pretty much done all the good biking there was to do in the area ?.
We were really going for it, and indeed I did attend another couple of rides later in the week that went elsewhere, but in general it was nothing like at good as they made out in the brochures.
Also bear in mind that the bikes can be shit quality. We did a ‘mtb’ ride to the top of the island, which involved height gain of around 1300m. The plan was to do some off road on the descent but my front axle seized completely about half way back, and the front wheel would only turn if the whole axle, QR and all, rotated. So that was the end of that ‘mtb’ ride.
When we returned to the Hotel, I asked the guide if he’d managed to fix the bike and he replied that he’d just stuck the wheel back on and left it at the back of the pile. It was nearly the end of the season and it would be someone else’s problem then.