I have to admit, that I just googled, what sanddollars are, and they look really beautiful. So I'm not sure, if they are too big, but they look like they would do a nice necklace.
As nobody needs 37 sanddollar-necklaces, she could also do some sort of wind chime (she could also add other stuff they found on the beach like shells...if they did )
Or she could paint them or just write nice quotes or stuff on them and hang them on the wall as a nice wall decoration.
It would be a nice idea to combine the sanddollars somehow with the honeymoon...but I don't find a good solution...maybe if you can glue some pictures of the honeymoon on the inside...but I don't know if it will work.
So I hope, I could help you/her and say her congratulations for marrying from me
And sorry for all the language mistakes, I really tried, but I'm just too long out of it