Hello
QuailyBirds;
Here are a few thoughts for you to consider:
First, South Africa Police Services (SAPS) limits the temporary import to 4 firearms per hunter, therefore if you plan on taking 5 firearms they cannot all be under the same name, therefore the same SPAPS 520. So, you will need two different SAPS 520.
Second, I do not know if you considered this, but no more than 1 of the 4 firearms may be of the same caliber, so if you and your sons are using rifles in identical calibers, this can be a further consideration. For example, if all three of you shoot your own .300 Win Mag, you will need three different SAPS 520.
Third, I do not know if you considered the ammunition question? The SAPS 520 is also the document that allows you to import ammo. The maximum is 200 rounds of ammunition per person per firearm, but this is not the issue. The issue is that airlines limit ammo to 11 lbs, including container and TSA lock. You will promptly reach 11 lbs if you accumulate the weight of an individually checkable ammo container (a requirement on internal flights in RSA) and a reasonable amount of ammo for several rifles/calibers. You likely want to consider that.
Fourth, are you sons legally allowed to own a rifle in the US? Age is of course a criterion, but there are other legal criteria that may apply.
If the answer is no, they will not get a US CBP 4457, the chain of custody will be broken (same name on US CBP 4457, passport, airfare / firearms checking tag, SAPS 520), and SAPS will refuse a temporary permit. You will need to go down to the maximum of 4 firearms on your own SAPS 520, and ammo will be scarce with 11 lbs. for 4 calibers.
If the answer is yes, then it seems easy. One would think 1 SAPS 520 with 2 rifles and ammo and 1 SAPS 520 with 3 rifles and ammo. But you said there will be 3 rifle cases, therefore the next consideration applies.
Financial consideration, if one person bringing 3 rifles in 2 rifle cases would result in checking a third luggage, you likely want to consider that the usual fee is for a third luggage is $200 (or more) with most airlines, while the fee for a pre-approved SAPS is generally in the $100 range. It is likely less expensive to do 3 SPAS 520 than 3 luggage, if all 2 of your sons can get a US CBP 4457.
In any case, my recommendation is to obtain pre-approved SAPS 520, this REALLY takes a lot of stress out of the process, therefore my recommendation is to use a South African broker like RiflePermits, Afton Safari Lodge, or others and follow their advice
I hope this helps...
Enjoy your Safari