If you want to give them a gift even when they say No Gifts, I think that's fine, what you have bought is not a very extravagant thing and if you think it's perfect for them then maybe it is. You know them both well, right?
HOWEVER, don't bring it to the wedding. Etiquette says the gift window is up to a year after the wedding. Sending it before just obligates them to say something nice about it and "thank you" at the wedding which is just one more thing to remember when what they should be thinking about is their marriage. Bringing it to the wedding also makes just one more thing that they have to schlep home. Same goes for cash or card or whatever else that could be misplaced on the big weekend. Finally, IMHO, cash for dear friends for second marriage is not appropriate, whereas a specially picked out gift (even flying in the face of the no-gift rule) says a very personal message along the lines of "I could not help but think of you when I saw this, I could not resist."
So send it after they are back home with a nice note about how much you love them both.
Have a great time at the wedding!