The barn boards could be an issue. If they came from a barn that had livestock in them, the sweat, urine and manure from the animals can saturate the wood over time even if those three things do not directly land on the wood. All seems well until you finish the project and your daughter brings it into her home and the heat begins to radiate that stench. A few years back, old barn boards were all the rage until some people started finishing their bathrooms with the stuff only to find out this problem.
If the barn has never had livestock in it though, you are good to go and should not have any problems.
As for a cheap dovetail saw...no joking on this...use a hacksaw if you need too. It works just fine, it just cuts slow.
I have no intention of traveling from birth to the grave in a manicured and well preserved body; but rather I will skid in sideways, totally beat up, completely worn out, utterly exhausted and jump off my tractor and loudly yell, "Wow, this is what it took to feed a nation!"