Donating it in-kind would mean he has 12 years of capital gains he wouldn't have to pay taxes on plus he could get the deduction off his income.

Assuming this isn't a lump sum he received this year as taxable income and without knowing his tax bracket, that's what I would plan to do with it if I knew I probably had to pay for a mission.

Worst case he could also start using it for in-kind tithing donations in 12 years to have a large tax savings in that area. He could then pay for college by putting money into a 529 and then taking it right out. He would still get the state tax deduction with doing that, but the money wouldn't be tied up for just college expenses until he knew he was going to use it for college. He essentially still gets the tax benefits of the investment growth too but donating the gains in-kind for tithing.