Carla,
First, if you are allowed 3 CHECKED bags per person and you have a family of five, the amount of luggage would be 15, not 18.

Secondly, SWA allows 3 checked bags per person. Yes, golf clubs can be considered checked.
Remember, there are size limitations to the checked luggage. It states that luggage SHOULD be locked, not that it has to be locked. I never lock my luggage.
The tags to put on your luggage are at the counter or at the curb check area. I grab a bunch so that I will be ready for the next trip and for the trip home. Also, I do not put my home address on the tags on the outbound part of the trip, I put the destination. I fill out the return tags the night before we leave for home.
You sure seem to be on the correct track here, and to help more, I have pasted the info from their website. Carry ons are limited in size, thank goodness, and they can be very strict about this and have seen them pull oversize stuff out of the line and gate check it, also, when the overheads fill up, they tend to do the same thing. I guess courtesy would be the rule here.
Hope this helps.
Southwest Airlines Baggage Information
Updated Travel Information
Updated: February 11, 2002
Checked baggage should be locked. Regulations require name identification on the outside. We recommend placing identification on the inside of luggage, too. Name labels are available at Southwest Airlines ticket counters. Carrier will not be responsible for money, jewelry, cameras, video and electronic equipment, silverware, negotiable papers, securities, business documents, samples, paintings, antiques, artifacts, manuscripts, furs, irreplaceable books, or publications and similar valuables contained in checked and unchecked baggage. Fragile articles and perishables are accepted as checked baggage only at the Customer's own risk. Checked baggage is subject to inspection and Customers may be required to present identification.
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Baggage Allowance
For each ticketed Customer, Southwest allows three (3) free checked pieces, with size limitations.
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Excess Baggage
Excess baggage will be charged at the rate of $40.00 each for the fourth (4th) and fifth (5th) pieces of checked baggage; $60.00 each for the sixth through ninth (6-9) pieces checked; and $110.00 for each piece checked thereafter.
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Weight and Size Allowance
Maximum weight is 70 pounds and maximum size is 62 inches (length + width + height) per checked piece of luggage. Overweight items from 71 to 100 pounds and oversized items (i.e., surfboards, bicycles, vaulting poles) will be accepted for a charge, ranging from $45.00 to $70.00 per item. Fishing rods will be accepted as baggage at no extra charge if properly encased in a manufacturer's container or for a charge of $10.00 if encased in a container furnished by carrier. Any item weighing more than 100 pounds must be shipped as Air Cargo, however, Customers cannot use SWA Cargo unless classified as a Known Shipper as defined by the FAA or FAA approved Indirect Air Carriers (IAC). For all Cargo inquires please call the Cargo Sales and Service Center @ 1-800-533-1222.
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Liability
Unless excess value is declared and charges paid at the time of checkin, Southwest Airlines' liability for lost, damaged or delayed baggage is limited to $2,500.00 per fare-paying Customer.
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Claims
Damaged or lost baggage must be reported, in person, within four hours of Customer's arrival at destination.
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FAA mandated carryon policy:
In keeping with new security directives from the FAA, strict limits are being imposed on carryon items.
Airline passengers may now carry only one bag plus one smaller, personal-type item onboard the airplane.
All Customers' and Employees' items are subject to a thorough, physical search.
Personal-type items include purses, briefcases, cameras, food containers, or laptops (case included).
Assistive devices for qualified Customers with disabilities will not be considered carryon or personal items and may be brought onboard the flight in addition to the above.
Southwest Airlines limits carryon bag dimensions to 10x16x24 inches.
On Southwest Airlines, a child restraint device for a child who has been ticketed or who has a seat reserved will not be considered a carryon or personal-type item and may be carried onboard.
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Animals
Southwest Airlines does not accept live animals other than animals trained to assist disabled persons.
Southwest Airlines does not accept pets for transportation in the cabin of our aircraft or in the cargo hold. Please make other arrangements for the transportation of your pets.
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For more information regarding Southwest Airlines Baggage policies, please see the Contract of Carriage.
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