I think it would be nicer for the boys to show up with something in hand, like a box of chocolates, a cake or pie, or some bakery cookies or something. Or cut flowers or a flowering plant. Having a floral arrangement delivered is inconvenient, and is obviously not a gesture from the boys. Plus, it is the rare floral arrangement picked randomly for a stranger that goes with the house’s decor, etc. And then the recipient has to send a thank you note to you, which is just a hassle. Just have the boys bring something that can be enjoyed by the group.
Oh, also, my daughter often invites friends from college to spend the night at our house and it is very, very rare for anyone to bring a hostess gift. And the sense is very much that she is hosting them, not me. Maybe I don’t see what they bring. Come to think of it, one of the kids that just stayed over spring break brought ice cream which was much appreciated.