good advice for the trunks, but what about the branches?
The branches should be marked with a black marker, if possible, as to the TOP. Branch wood makes the best bows, and the top of the branches make the best backs. I have seen yew trees with arm-thick branches 20 feet long, practically free of knots. Goldmine of perfect bow wood. For branch wood, cut it into the largest useable sections you can. I usually cut all my staves overlength, and don't bother sealing the back. When time comes to start carving, i locate the center of the grip, measure out the bow from there, and cut off any checking in the process.
May i ask you, if you have 3 yew trees on your property, just cut one? Or take the branches? It's great wood, but a rare tree. The branches are the best part anyway. Not to rain on your parade, just saying.
good luck!