Both hookers have previously trained with Gregor Townsend's national squad, but the three-match tour is expected to provide each with a first Test cap.
Scrum coach Pieter de Villiers believes the pair are ready for the step up to international rugby, praising how quickly they have settled into the Scotland camp after their standout club campaigns.
Ewan Ashman is widely expected to start against Argentina on Saturday, with Hiddleston in line for a place on the bench, while Stephen is anticipated to get his opportunity in the final fixture against Fiji at Murrayfield.
Asked how the two hookers have adapted to life in camp, De Villiers said: "Really well. They've done so well with the club throughout this whole season. Showed a lot of maturity, I thought, with Glasgow.
"They've really settled in very quickly with the group. Training well. So we're looking forward to seeing how they get on in this next stage of their career, but they've been impressive.
"Obviously, the only way to get Test-match experience is by playing Test matches. All players who today have got 100 caps have started at some stage with their first cap.
"So we do feel confident that they're ready for it and that they'll grow quickly and make strong strides with this group and play rugby at this level."