Hi
WE have 4 and 1 on the way ranging from 1 to 10.
We don't use the older ones to help with the younger ones unless they want to, but often I find they do, especially the oldest helping out with the youngest at mealtimes, bath time etc.
I find the only way to make it work is to be meticulously organised and build a good support newtwork.
I know you say you have no family nearby, what about friends? I plan week ends in advance and try to make sure there is a mix of family time and individual time for each child. Good activities to do together are swimming (though I do find the getting dressed/undressed VERY testing! :O/ ), a trip to London or a cycle ride (sometimes dp will take a longer route with the older ones and I'll take a shorter route with the youngest to accomodate the age difference).
The middle 2 are both boys and have similar interests so I might arrange a playdate for them at a friends while I do something with the oldest and dp does something with the youngest. I might get one child to help me make breakfast, a different one to help with lunch and another to help with dinner while dp plays a game or something with the others so that each child gets 1 to 1 time.
I also don't think there is anything wrong with one parent taking one child for half and hour or so and telling the others "this is so and so's special time with Daddy. We are going to do x but this afternoon, you will have special time with Daddy as well".
Use bedtimes to your advantage as well - the oldest stays up later than the younger ones so she gets her special time with us then. The boys usually wake first, so I might go and play a board game with them while everyone else is still in bed.......
It does take hard work and effort though and I DO have the odd day when I just want to lock myself in a room to get away from ALL of them. What I wouldn't give to be able to have a wee in peace sometimes......
SG