So, Matthew and Elliott don't mean anything to us - we just like them! Russell is my father's name. We definitely want Elliott in there, but which one would you go for? (Also, we want the double 't', it goes better with the double 't' in Matthew and the double 's' and 'l' in Russell)
That does make me think - should I then use both of his grandfathers' names? I just don't think it goes as well as Matthew Elliott Russell... Or should I save his other grandfather's name, just in case we have a DS2?
We gave our dd two of her great grandmother's names, and our ds names that we liked with no family connection. They both seem happy! Weirdly neither my mother or my FIL were particularly pleased that we used their mother's names for dd. Apparently neither liked them very much!
I'd just pick the names you like. Personally as someone who has two middle names I find it a bit of a nuisance as often you have to drop one of them (or one initial) so for example having bank accounts etc with two middle initials can be impossible. I tend to drop them both now unless I can use them both as my name looks all wrong with just one of them. Trivial issue mind!
Are you planning on multiple children Jassy? If not then you won't be able to honour all the grandparents. Might be easier to avoid upsetting the ones that you leave out by choosing neutral names instead.
If it's an expectation I'm not sure it's really an honour anyway. Is it a family tradition?