Why not consider a CASE Mini Copperlock? It looks Old School but it locks, so people who are unfamiliar with slipjoints will be OK. Easy to open but un-menacing.
The knife is nice and slim so it won't be a drag in the pocket but at about 3.5" closed it's still credible.
CASE make these in dozens of different handle choices too and they look decent not cheap in anyway. The cost is not too high either. Last word, I'd suggest you include a card with each knife, signed with your personal thanks. I think it could actually be better than having them engraved, myself,I don't like any engravings on my knives but that's just because I'm a knife addict....