The wedding is about eight weeks away most plans are in place. Since the wedding is small we are only having his son and daughter stand up. Not sure what to get them.

They are very excited about the wedding and we all get along well. They are young adults finishing college any thoughts?

Do you have a price range in mind for the gifts? My husband and I gave personalized gifts for our wedding party. The Knot has a lot of gifts you can choose from Wedding Favors - Wedding Favor - Wedding Favors Ideas. Things Remembered also has a good selection of gifts you can have personalized Things Remembered - Personalized Gifts and Unique Gift Ideas to Celebrate Life's Moments

So I assume he has two children already, so how old are they?

Early twenties

Well I think something like a meaningful pendant for each of them would be nice, or something that can be put on display. Something nice, but not super expensive or anything. I'm not sure on specifics because they're older and I don't know their tastes, but I have a feeling that once oyu find soemthing you'll know. :)

I would suggest a piece of gold jewelry for each of them if that would be affordable - perhaps cuff links for the son and a locket for the girl with a chain. Both could be engraved with their initials if you wish.

I bought our best man 2 tickets to a pro baseball game -- he was so happy he could use it to have a day out with his son, rather than something to sit on a shelf.

I gave my maid-of-honor a print of a painting she had admired and a movie theater gift certificate (with enough $ on it to buy snacks and take a guest)

Not particularly "personal" but a handwritten thank you note can accomplish that. They were both very excited to have a "free" night out to have some fun. :)

They are in their early twenties. I am leaning toward an engraved gift of somesort. A locket for her perhaps .For him I am not sure .Thanks for all your ideas