Does anyone else have problems with their kids and eating? My 5 yr old daughter is a complete nightmare!!!

She's growing like a weed so i'm not completely going round the twist with worry but i am concerned. I've tried everything from devising a ' little, medium, big ' effort which has its own 'rewards' for big efforts, like a treat before bed etc..for little efforts, its no treats at all! That sort of works but when it doesnt, i divide her food in half on her plate, then say she has to eat one half and once she has, we talk about the other half...and she generally eats a little of that half...then recently i've really had to get tough and tell her that she'll get the rest of her dinner for supper if she doesnt eat it.
This has been going on for well over a year now, if not longer. She's naturally a little dotty anyway but she only weighs 2.5 stone at the age of 5 but she's constantly on the go. I have noticed that she'll eat 'little and often' but doesnt want to sit down and eat a whole meal. I dont overload her plate and sometimes she does clear her plate. When she does, i go a bit over the top with praise but it does work as she feels very grown up then.
Anyone else have nightmare meal times???