So I am working on scripting a stage/parlor performance just for the fun of it, and I have tried to work my tricks down to "the best" and order them in the best way possible. However, right in the middle of the performance, I have a situation where it is the ideal time for the spectator that I've been working with for the past few tricks to take a rest and head back to their seat. However, immediately after that, the next few tricks require a spectator's help as well.

I have thought about re-working my trick order to create a larger break between the two sections, but I cannot think of anything. Of all the tricks I know and can do well, nothing really would fit in here. Basically, the first half ends on a 3-Fly, and the second half picks up on an ACR. I don't think it would be a good idea to use the same spectator for all the spectator-involved tricks, but I could be wrong.

I've thought about using a magical "interlude" of sorts. Something quirky and goofy like SilkCola to earn a few laughs as I'd need a "snack break". Or even an intro card trick. But in my mind, there would need to be a reasonable amount of time distance between the first and second spectator. If it was a Magic Castle-type parlor situation, with two spectators already up front, this wouldn't be so much an issue.

What do you think? Would having a single spectator up there most of the time diminish or help the performance? How would you handle the transition if there needs to be one?

First, what is the time frame of the whole act?

Second, you mention "...time for the spectator that I've been working with for the past few tricks to take a rest...", it is my opinion that if that person needs to take a rest, so does everyone, it's time for an intermission. By that, I am suggesting that once that person is dismissed, you do something that is a little slower that involves the whole group.
(Listen to some Beethoven, Bach, Chopin, listen to how the tempos change in one of compositions and how you react to them. )
After 'intermission' speed up your tempo and get a new helper.

^Good thoughts. I've only got about 30 minutes of material currently. It's short and sweet. I don't mean real tiredness, just that I think the first spectator has "done enough" and it is time for someone else. I like your thinking on the intermission, which I why I think something like SilkCola would work well here.