In the past I've had a strict policy of only selling to individuals holding a current Concealed Carry Permit... Most buyers in Texas that would be interested in paying a good price for your guns probably have one.
How old are the shotguns?
Most shops will not tell you what the gun is worth, but will be happy to sell on consignment. I have sold in the past through Bullet Trap in Plano, but only because they offered to do a zero-fee transfer applying the price of the sold gun to the purchase of a new gun. Not sure what their consignment policy is generally.