I bet it will be fun. I have found the best way to deal with teens and toddlers is to be very direct and tell them what you expect and offer fun rewards - like a movie out. Teens are so great with little kids - they just need to be reminded sometimes
You can make popcycles with the younger 2 while the teens veg and let the little kids "serve" the big kids when they are done. Also, water ballons are cheap and fun - getting everyone out to play in the water for a while so that you can re-group. Enjoy these fun family times - they are too few and fleeting!