Hi Betty.
Greyhounds do make gentle pets as a rule and certainly have a quiet elegance. But, like all dogs, the breed is far less relevent than the individual animal. Whilst we can generalise and say, for example, that collies need a lot of exercise or that St Bernards need less than a Whippet, what really counts is the attitude of each dog (I speak as the owner of a stroppy Lab and an-over friendly GSD.... but hang on, isn't that normally the other way round?!).
If I am brutally honest the one thing which concerns me is your question as to whether Greys are noted for their tolerance. I always get a bit worried when I hear this sort of remark as I think oh no, they're looking for a dog that the kids can "climb all over", which I would NEVER advocate. If - and forgive me please if this isn't the case, but IF you think that a dog in your home would have to display tolerance because the children could be a bit hands-on/full-on, I'd seriously advise that you hold back from owning a dog for a few years for the sake of all concerned.
That aside, the best thing to do is to consult many rescues, breed and all-breed, the big ones and independents and give yourself lots of time to ask questions and to ensure you have the perfect match.
A good rescue won't only neuter, vaccinate, chip etc but will also offer lifelong advice and support and will match you to the right dog - or be honest and say that they haven't got the right one for you, rather than encourage you to take anyone.
I'd also advise you to join the forum of LurcherLink as I'm sure you'll enjoy Kay's expert advice on all things pointy.
Good luck!