During a long meeting, your attendees need to be "re-energized" at times. And since they are meeting face-to-face, you should take full advantage of it and get them interacting. This will ultimately make it easier for them to be a more effective team. 

If the weather is nice, get them outside and give them a short but fun team challenge. Here's one that is easy to do indoors or out, and you don't need elaborate equipment to do it...just some space.

Give each team of 8-10 people four sheets of newspaper: 2- are from the regular news; 1 is from the comic section; 1 is from a full page advertisement (like Frys or a car ad). Instruct the team that their challenge is to get everyone from point A to point B (which is a distance of about 30 feet away-- which you can mark with chairs if you don't have cones or other markers) without stepping on the ground-- only stepping on the newspaper. HOWEVER- only up to 3 people may stand on the plain newsprint sheets at any given time; only two may stand on the sheet of advertising at any given moment and only one person may occupy the comic strip sheet. They will need to figure out how to get their entire team across the 30 feet, keeping these rules. Yes, under these guidelines not everyone will be able to go at once, and one person will need to work his/her way back to the rest of the group (so they can get across) --also stepping only on the newspaper. They need to make sure they don't tear the newspaper, and that can be a challenge in itself. If you have time to buy materials, you can also use  different colored or sizes of hula hoops,  24" square foam pads (usually for kids' play areas), giant trash bags or large sheets of cardboard. You just need to make sure that two out of the four items are similar and the other two are distinctly different. You can use markers or colored tape to distinguish them. Also, newpaper does not work well on a thick lawn or sand.

Give the teams time to strategize before starting the "race." It takes communication and a clear plan that everyone agrees to. People will be up, moving around, trying different ideas and working together in a fun, spirited yet short event. They'll go back to the meeting invigorated and having learned something about their teammates.