Hello Caw1,
Please don't split up a set of medals or separate the originals from the citation. You've had the medals since your father's death and you have a son who knew his grandfather to pass them on to.
I assume your father acquired the miniatures in his lifetime, so are personal to him, unlike replicas that you could buy. Why not have a display case made up using the miniature set along with a good copy of the citation etc. (Make it clear this is a copy either by copying it on a smaller scale or marking it as a copy) Include photographs of your father, especially if you have one of him in uniform and/or wearing his medals. Add details: date of birth, date he enlisted, Regiment he served in etc. Add that the medals are miniatures of the originals (Like the originals, do they have his name around the edge?)
There are companies that specialize in this type of display and could advise you. Might be costly but personally, I would be delighted to have my grandfather's WW1 medals, even in miniature form, especially presented in such a lovely way. (My grandfather's 'Death Penny' was split from his medals and is now lost, which is why I said, "don't split the set up."
This is just an example of the type of display I mean.
www.ebay.co.uk/itm/YOUR-MEDALS-FRAMED-ARMY-NAVY-AIRFORCE-MEDALS-PROFESSIONALLY-FRAMED-FOR-YOU-/221732316539 Treasure your father's medals. They'll keep his memory alive down the generations.
Regards, Dod.
PS. 2nd Hand medals can be easily bought but they will have a soldiers name engraved around the edge.
Added: Some new post while I typed this so display case for either your son or half brother!