Minimizing Estate Taxes through Gifting

John is a 65-year-old retiree who has accumulated a substantial amount of wealth over his lifetime. He has three adult children and wants to ensure an equitable distribution of his assets upon his death. John is particularly concerned about the tax implications his heirs might face regarding his estate. He is considering various estate planning strategies to minimize these taxes.

Which of the following estate planning strategies would most effectively help John minimize the estate tax burden on his heirs?