Expect the line to be VERY long. When they were at DTD last year we went on the 1st day they were there and got there at 5:15pm and we were about 25th in line, the M&G was at 6:00pm. But I saw where people waited 3 HOURS on the 1st day. They were spending a lot of time with people, I would say 4-5 mins per family. We got Character interaction, Individual pictures, group pictures, autographs, and photopass pictures. I read where they cut out Autographs and individual pictures on the other 2 days because of the large amount of people coming to see them. The 1st day no one had chairs, but the word got out so people brought chairs for the other days.
Now DTD is free and a party is not but I'm sure the lines will be close to 2 hours if I had to guess just by judging by the line for the 7 Dwarfs so if you are wanting to meet them, I would get line around 6 if possible.