I wouldn't have done a DW without using a TA. Takes most of the stress off of you and gives the guests someone to ask the millions of questions that they all will definitely ask! My TA is a friend and she cc's me some of the questions. People I never thought were high maintenance, turned out to be when it came to just putting down a deposit!
Plus, if you have a good experienced one, they'll get you the best rates and perks for your business. Doesn't cost you a thing to use them. Also, if something (GOD FORBID) happens where the flights are cancelled, when everyone uses the same TA, they can rebook you and keep your group together.
They're WELL worth it!