Ratter I totally understand where you are coming from. The exact same thing happened to Mr. Aprilis. In fact it was the Easter Bank Holiday weekend 6 years ago that it happened.
We had not long moved house and we just wanted a quiet weekend. No going away, no having guests to stay. Mr. Aprilis's brother did the same thing; rang to ask if he could come and stay for the weekend and we said we would rather he make it the May Bank Holiday weekend instead. After all, it was only a couple of weeks away (that year Easter fell in the middle of April).
On the Tuesday when everyone went back to work, my Bro-In-Law phoned in sick and was found by his girlfriend when she returned home from work at the end of the day. He had locked himself in the garage and put a hosepipe on the car exhaust. He was found in his pyjamas and had apparently been there all day. The next door neighbour had been knocking on the door because he could hear the engine running and smelled petrol fumes but got no answer. He tried the garage door but it was locked so he couldn't do anything. It was horrific.
So many times we have wondered if we had let him come to stay would we have prevented him from doing this to himself. Or would he have done it anyway later on? We have beaten ourselves up for years over it. The worst thing about it was that to this day nobody has any idea why he did it.
Despite what I said previously I think I would definitely change the decision about that weekend even if it wouldn't have made any difference in the long run.