Part A - Hire your own real estate appraisal. You would be under no obligation of any kind to disclose the results of it to anybody.
Part B - Hire an outside, unbiased, third party to, on behalf of the both of you, hire an appraiser and be the appraiser's client. The deal is neither of you get to question, pressure, or even speak to the appraiser. Pay the third party to do all of that on your behalf.
Part C - Negociate
Part D - based on failed negociations.... put the real estate on the open market. Better yet, go find somebody rich that really hates this golf course owner and see what he or she might be willing to buy the land for.... :icon_mrgreen: If you get an offer from them, go ask the golf course owner what it's worth to him now....