Is there a mod that stops the newly-arrived Sims on an outing from interrupting whattever my Sims are doing with queue-stomping Talk interactions? It's so annoying, and when you try to cancel it out they just do it again and again!

Maybe, though I think the initial chat might be required in order for the newly arriving sims to join the already existing group. One approach, which of course doesn't work if your own sims are already grouped or out and about, is to invite the other sims over to their home first and then go on a group outing together from there using Go Here (or Go To Lot) With...