Dooyooers who've not yet been converted to the quasi-relgion that is model railways will probably wonder how a few little bits of plastic could sell for £7 on Amazon. As a keen enthusiast of model railways, even I was a reluctant to part with my hard earned money for what is a, if nice, expensive detail.
As with most Hornby products, these 00 gauge gravestones are by no means the most well-designed and detailed products on the market. they do, however, benefit from reasonable design, a decent finish and some nice detailing.
On the child friendliness front, be careful with small children. My two year old liked to pick these little pieces up a lot (even when they'd been glued into a gaveyard scene by my six year old son). That said, since the gravestones are all single piece products, there is no risk of breakage.
If you can afford the luxury, buy the church and a few trees first. If not, I would suggest investing in something a bit more substantial, or to scratch building (which is far more fun).