Regulation 213 (e) f the National Road Traffic Act 93/1996 states that no person shall operate a minibus or midi bus, first registered after 1 January 2006, operating in terms of an operating licence issued in accordance with the provisions of the National Land Transitional Transport Act, unless seatbelts are fitted for the driver and all passengers.

If the vehicle is not operating under this licence then it is not required to have seatbelts for all passengers but for the interests of road safety and the protection of the children if the school wishes it can have seatbelts fitted for all passengers.

223.     Overall width of vehicle
 
No person shall operate on a public road-
 
(a)     a bus of which the distance between the centre-lines of the tyres of the two front wheels exceeds one comma nine metres, if the overall width of such bus exceeds two comma six metres;
 
(b)     a goods vehicle the gross vehicle mass of which is 12 000 kilograms or more, if the overall width thereof exceeds two comma six metres; or
 
(c)     any other vehicle, if the overall width thereof exceeds two and a half metres.
 

Firstly make sure that you check the authenticity of the officer by asking him or her to produce an appointment card. If satisfied comply with their instructions. If you feel that you been harassed or ill treated in some way I suggest you a lay a formal charge and submit a written complain to his or her seniors. Closely follow what steps have taken to address your concerns.

Bottom line (the rules pertinent to this question):

You may not park:
•    where it would cause a danger or obstruction to other traffic;
•    where it would obstruct other traffic wishing to enter the road from a private or public entrance;
•    on a road less than 5.5 metres wide

Relevant text per the Road Traffic Act, Rules and Regulations:

304.   Stopping of vehicles

Except in order to avoid an accident, or in compliance with a road traffic sign or with a direction given by a traffic officer, or for any cause beyond the control of the driver, no person shall stop a vehicle on the roadway of a public road—

(i) in any other place where the stopping of a vehicle would or would be likely to constitute a danger or an obstruction to other traffic.

305.   Parking of vehicles

(1)  No person shall park a vehicle on a public road—

(b) in any place referred to in regulation 304 (i.e. any No Stopping area);

( f ) in such manner as to obstruct any private or public vehicular entrance to such road.

(4)  No person shall park a vehicle on the roadway of a public road within an urban area—

(e) which is less than five and a half metres wide unless the public road concerned is restricted to vehicles moving in one direction and such parking is permitted by appropriate road traffic signs.

This is correct. The maximum width that a bakkie can go up to is 2.5m, but manufacturers make them smaller.