You might want some strong branches since you'll be using them as hand holds in a rather aggressive fashion as a newly wed, just sayin. Bed bolts are a good choice for connecting head and foot boards to the bed frame. They will allow you to tighten things up as the wood changes with humidity, lessen the squeaking, as well as allow taking the bed apart for moving. One issue may be finding 4x4s that are dry enough so they won't twist, warp or check. Looks like a white pine frame. I'd probably go with 1 1/4" hickory branches.