My chorus is performing a song in which 8th notes are swung. But at times there’s a “rest-note-note” triplet. Should the two notes be swung?
yes, triplets are swung unless there are staccato’s expressing otherwise
Yes. It would be jarring to the rhythm of the piece to not swing just those two notes. You going along, swinging, swinging and then dut-dut, then back to swinging… and without the staccato notation, I’m pretty sure that swing feel is what the composer wanted.
Is the triplet group 8th notes?
I’m visualizing something like:
eeeeQ(ree) | eeeeeeee | Q
where e is an 8th, r is an 8th rest, Q is a quarter note and the () indicate a triplet group.
If so, it would be played like:
EeEeQree | EeEeEeEe | Q
where E is given 2/3 of the beat and e 1/3 (swinging eighth notes). The r is 1/3 of a beat. And when I say beat, I mean quarter note. I hope someone can make sense of what I’m trying to convey 
So, if this is the case, no they are not swung because they have been fully written out in the triplet notation.
If I’m understanding it correctly, and it’s notated as a triplet, no.
One way to think about it is this:
Instruction to swing the 8ths is roughly an instruction to treat 8th notes like sets of triplets, with the first two notes toed together. Depending on the style that description gains or loses accuracy, but it’s sort of right. It’s just a lot visually easier to say “swing the 8ths” than to write out a whole piece in triplets.
So, if you approach your swung 8ths that way, a written out triplet should fit quite easily into your rhythmic counting, since swung 8ths are also triplets with the first two notes tied together (instead of saying “tri-puh-let” you say “tri – let”).