The 18-year-old Maphaka was named player of the tournament at this year's U19 World Cup in South Africa and later landed a contract in the Indian Premier League, while hard-hitting middle-order batter Smith impressed with both his batting and bowling in domestic T20 competition.
The 15-man South African side return to the Caribbean after finishing runners-up to India at the T20 World Cup in June but with a changed squad that is without several key players.
"Several players were not considered for this series due to either injury, being in a conditioning block that is related to workload management, or their participation in ongoing T20 leagues," said coach Rob Walter.
"This tour allows us to continue developing our player pool whilst maintaining the core of experienced players. It will also expose our emerging talent to quality international opposition, similar to the last time we played against the West Indies in May.
"Kwena has been identified as a player with significant potential, and this tour presents a great opportunity to include him in the Proteas environment and gain valuable international experience," he said in a statement.
There is a recall for Rassie van der Dussen, who was a surprise omission from the World Cup line-up.
The three matches will all be played at the Brian Lara Cricket Academy in Tarouba, Trinidad and Tobago on August 23, 25 and 27.
Squad: Aiden Markram (Titans, capt), Ottneil Baartman (Dolphins), Nandre Burger (Western Province), Donovan Ferreira (Titans), Bjorn Fortuin, Reeza Hendricks (both Lions), Patrick Kruger (Warriors), Kwena Maphaka, Wiaan Mulder (both Lions), Lungi Ngidi (Titans), Ryan Rickelton (Lions), Jason Smith (Dolphins), Tristan Stubbs (Warriors), Rassie van der Dussen (Lions), Lizaad Williams (Titans).
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