Gifting/Discounting a Rental Property to Children

[NA NA]

Hi, I'll try and keep this short, but I'm a little clueless.

Backstory

I own a rental property that I want to sell to my son and his wife. The property is worth around 100k, but I only want to sell it for 40k (the remainder of the mortgage).

The problem is that if I give it to them for 40k and they ever sell it, the capital gains taxes would be significant.

Is the following a realistic scenario?

1. My wife and I gift them $56,000. Using gift tax rule, we can each give them 14k in a given year. So 14k x 4 = 56k.
2. We sell the house to them for $96,000.
3. They use the $56k as a down payment.
4. Leaving them with the $40k mortgage.

Again, I'm in over my head here, so I don't know if this is even feasible. 

Any help would be greatly appreciated! Thanks.