M.B.
I probably don't have the sort of advice you're looking for as both my kids pretty much were the same way. Some kids just need more attention, one on one time and comfort from mom. This is particularly difficult when mom works - even at home. So, I found it easier to give in and everyone got the sleep they needed - indeed, I got some extra naps that I wouldn't have taken otherwise as I would often fall asleep with them.
The one thing I can tell you is that while some might call this a bad habit, it does not last forever and with my kids, once they reached the point this was no longer necessary, we NEVER had any issues with them getting up at nite. One thing that did help us was the nighttime CD by JIm Weiss - it's stories and the tone of voice is incredibly soothing - it puts me to sleep.
And, again, I think this varies per child, so don't feel bad that this is what your child needs. My 13 year old son would actually still like me to lay down with him at nite and he is the most independent child you can find, so it's not that he's a mama's boy, insecure, a wimp or whatever. He just has a strong need for physical closeness and attachment. My older son wouldn't even consider allowing me to do this by the time he was 7 or 8. Listen to your instincts and do what's best for your child - this isn't manipulation of any sort - this a child naturally seeking closeness and attention from their parent(s). I have found that when you meet these needs when they are young, they end up more independent, mature and self confident as teens.