I've brought back wine from Europe very safely with those padded suitcase shipping products, but before I had those, I did well with just a really good packing job. That box looks pretty good, but just to play it safe I'd still cushion it on all sides.

One thing to note - if you pack it well, you should be fine, but you may want to but a plastic bag around the champagne OR whatever else is in the suitcase...just in case the worst should happen.

Congratulations, and have a great time!