Let me start off by saying: I do fully intend to tip my vendors, and tip them well (just so we don't have any confusion)...
But when it comes to things like DJ, Photographer/videographer, ceremony musicians, Waitstaff, etc... I guess the standard practice is to put money in envelopes that you give to the best man/maid of honor/father of the bride, etc to give to vendors at the reception. Thing is, in order to do that, I'd need to know how much to tip even before my wedding day, and if that's the case, I'd have no idea of how much to tip because I haven't seen them in action yet. I don't want to over tip a vendor who may have messed up, or under tip a vendor that went way above and beyond my expectations.
Would it be acceptable to mail tips to the vendors a few days after w/a thank you card? I already have the vendor thank you's pre stamped and pre addressed to avoid forgetting.