It is definitely more convenient to order the gift online and get it shipped instead of carrying it all the way to the wedding. This mostly applies to gifts that are not gift cards and the like. It is just a more convenient and hassle-free process to ship it to the couple rather than carry it along all the way to the wedding and then have them carry it all the way back. Plus, you need to think about the extra baggage charges that the newlyweds might incur if they have to come back with so many gifts. The best thing to do would be to ask them what they would prefer.