Very nice looking bed.
As for the glue up issue, you're right. You can never have too many clamps. One thing you could do to help with alignment is to drill a couple of holes for short dowels for alignment. Once you glue them in, they'll be like the rest of the wood. Another thing would be to leave the pieces a little long--you should do that anyway when gluing up like that--and using small nails driven in and their heads cut off. These will prevent the pieces from sliding while the glue is wet and they can be cut away when the piece is trimmed to length. Just make sure you know where they are so you don't hit them with the saw.
If you have access to a jointer, you could just leave the pieces over wide, too. Then, after gluing up you can true all the faces.