i had some which had been spoiled by the rain in my sons playpit.
i mixed it in the top inch around my box hedging.
they appear very well on it!

If is appears to be soft sand, then don't use it as it will compact and not allow the soil to drain. If you do have to use it, then spread it very finely over a large area. If it is a coarse sand then it will be O.K. for general use.

Mix in a small amount of compost and you have good seedling mix. Seedlings root better and they come out of the mix with almost all their roots intact.

One of the panel on GQT last week (on iplayer) said if you put the play pit on the lawn the sand that the children throw out would aerate it for him
?

I wouldn't throw it away - playsand is usually silver sand, and that's useful for making up a mix to root cuttings in, its a good substitute for 'horticultural' sand.

I wouldn't use it on the lawn if it's the fine sand that is usually in kids sand pits. I don't really know why but the sand my daughter broadcasts across the lawn seems to lead to bald patches. ( Even if I rake it daily). Maybe it's just killing the moss but it clumps when wet and I'm sure it isn't aerating the lawn.

I wouldn't trust the panel on GQT either as they don't have access to google during recording.

I'm a bit mystified as to why anyone would think spreading sand over a lawn 'aerates' it. Usual procedure if adding sand is to spike the lawn closely all over, then brush sand into the resulting holes, but even then, it's proper lawn sand, which isn't the same as play sand or silver sand, has other ingredients and controls moss.