Oh don't get me wrong demi, loft bedrooms are awesome. But when I think of a 3br with a loft br, I envision a master suite where two bedrooms are down stairs and the King and Queen (homeowners) reside over the home on the floor above looking down onto the subjects (guests or kids).
I know its a bit romantisized but I just don't buy a loft guest bedroom. I mean if there is only a little space for a daybed, then I can only imagine that the loft bedroom is not the only bedroom on the second floor.
So I just picture myself as a guest laying in this "guest bedroom" as other people walk upstairs towards their actual rooms with me laying in bed and no walls. Kinda creepy. I know ultimately when you have kids a Loft master suite may be impractical but at least that looks functional for a while.
Some stuff to consider if you are still designing this house. I hope it works though and I as long as you like it that is all that matters. Good Luck!