Simply replacing the first receptacle in the group with a GFCI receptacle, will provide protection to the entire group (if wired properly).

GFCI Receptacle

Locate the feeders

WARNING:

This procedure should only be carried out by persons with the proper tools and knowledge. And should be carried out with extreme caution.

When you open up the box containing the first receptacle in the group, you're going to notice two cables enter the box. One cable brings power from the breaker/fuse box (feeder), and the other carries power to the remainder of the circuit. You'll have to figure out which cable is which, so you know how to connect the GFCI receptacle.

1. Start by turning off the power at the breaker/fuse box.
2. Disconnect the receptacle, and position all the wires so that they will not contact each other or anything else conductive.
3. Turn the power back on.
4. Using a multi-, voltage or non-contact meter determine which set of wires is which. The feed from the breaker/fuse box will have power, while the line going to the rest of the circuit will not.
5. Mark the wires in some way, and turn the power back off.

WARNING:

If you got a voltage reading on more than one set of wires, STOP, do not follow the rest of these instructions. contact a local Electrician.

Connect the GFCI

On the GFCI receptacle you'll notice that one set of terminals is labeled "LINE", and the other is labeled "LOAD".

1. Connect the wires from the cable you marked as being from the breaker/fuse box, to the terminals labeled "LINE" (Black to brass, white to silver, green/bare to green/ground and the box if it's metal).
2. Connect the wires from the other cable to the terminals labeled "LOAD".
3. Install the receptacle into the box.
4. Turn the power on.
5. Press the Reset button on the GFCI receptacle.

WARNING:

If the receptacle will not reset, the wiring is connected incorrectly, or contains a fault. Contact an Electrician to complete the job.

GFCI Breaker

Alternatively, you can install a GFCI breaker to protect the entire circuit.

WARNING:

This procedure should only be carried out by persons with the proper tools and knowledge. And should be carried out with extreme caution.

1. Turn off the breaker.
2. Remove the black wire from the terminal on the breaker.
3. Locate the white "neutral" wire associated with the circuit (should originate from the same cable).
4. Remove the white "neutral" wire from the neutral bus bar.
5. Remove the breaker (Caution should be used not to touch the hot bus bar while the breaker is removed).
6. Install the GFCI breaker.
7. Connect the white wire from the GFCI breaker to the neutral bus bar.
8. Connect the white "neutral" wire from the circuit to the GFCI breaker.
9. Connect the black "hot" wire from the circuit to the GFCI breaker.
10. Turn the breaker on.

WARNING:

If the breaker will not reset, the wiring is connected incorrectly, or contains a fault. Contact an Electrician to complete the job.

Test the GFCI

Once the GFCI device is installed, it should be tested at least once a month to insure it's functioning properly.

1. Press the Test button.
2. Press the Reset button.

If the GFCI will not reset, the GFCI is bad, the wiring is incorrect, or there is a fault. Correct any faults, and/or install a new GFCI device.

This was something the builder just did (I wouldn't even call it convenience/cost, for that matter).

We start with 210.52(B)(1):

(1) Receptacle Outlets Served. In the kitchen, pantry, breakfast room, dining room, or similar area of a dwelling unit, the two or more 20-ampere small-appliance branch circuits required by 210.11(C)(1) shall serve all wall and floor receptacle outlets covered by 210.52(A), all counter- top outlets covered by 210.52(C), and receptacle outlets for refrigeration equipment.

and 210.11(C)(1):

(1) Small-Appliance Branch Circuits. In addition to the number of branch circuits required by other parts of this section, two or more 20-ampere small-appliance branch circuits shall be provided for all receptacle outlets specified by 210.52(B).

Between these two sections, we can establish that the dining room outlets are part of the small-appliance branch circuits, not the general lighting load.

However, 210.8(A) point 6:

(A) Dwelling Units. All 125-volt, single-phase, 15- and 20-ampere receptacles installed in the locations specified in 210.8(A)(1) through (10) shall have ground-fault circuit- interrupter protection for personnel.

(6) Kitchens - where the receptacles are installed to serve the countertop surfaces

requires only that the receptacles installed to serve the countertop surfaces in the kitchen be GFCI protected. This means that no other receptacles on the small appliance branch circuits require GFCI protection under the 2014 NEC, regardless if they are located in the kitchen proper or in a separate dining room.