I had a look on the code of oqueue to get me started, and it was a sick amount of code. around 26000 lines and 850.000 characters.
Now oqueue contains many options and shit, and the creator seems to be of the object-oriented school, so the code is alot longer than it could have been, but it's still a much bigger project than i had expected.
Unfortunately don't have the spare time to do anything at the moment, but will update the thread once I get going.
sorry for not reading this now but the simplest way for you to deal with people not logging on would be to put a few buttons like "hopping over now" , "be there in 30", "something came up"
an have it display what people chose so everyone can see that way if 3 people choose "something came up" you can just reque.