I haven't btdt, but I think your analysis of the pointlessness of forcing him is right. His analysis is right too - he wouldn't be just visiting, he'd be putting his foot on the slippery slope. Moreover, if you force him, it goes badly, and then a year from now you both really want to switch school, you're in trouble. I'd be upfront with them: "DS is so distressed at the idea of changing school right now that you wouldn't get a true imoression of him, and it would be wrong to forge ahead anyway. So sorry for the sorry notice but we must pull out. We're really impressed by what we've seen and we may be back." or whatever. I'd also be upfront with him: you make the education choices, but you understand his position, and he should let you know if he wants to talk about maybe going to the other school in future.
