The reading of the “whole megillah” is a rather lengthy process, and it can be difficult for children to sit through the whole thing. Furthermore, when Purim is on a school night, some families may want to come for the Purimshpiel and still get their children home at a reasonable time. Is it permitted to start the Megillah reading, perform the Purimshpiel in the middle of the Megillah reading, and then finish the Megillah reading afterwards to accommodate those for whom this is an issue?

Response:
At first glance, it might seem this should be permitted: the Shulhan Arukh records in OH 690:5 that it is permitted to interrupt the Megillah reading, even if you paused long enough to complete the Megillah reading. The Rama adds even if you have a conversation in between, it is permitted.

However, there are several sources which would cause us to conclude that for the purposes set out, such a lengthy break is not permitted.

The Rama on OH 690:5 adds that we rebuke someone who converses during such a break, because, as stated in OH 692:2, we don’t converse during the reading. The Mishnah Berurah adds neither the reader or someone listening should converse during the reading, not even words of Torah, although after the fact, such a person has still fulfilled his obligation as long as he heard the full Megillah. And Mishnah Berurah states there are certain form of conversation that are permitted, such as greeting someone between the chapters, as we have with the reciting of the Shema.

Mishna Berurah also brings a teaching that since you have made a blessing on the Megillah reading, you should not pause in the meanwhile until after completing the mitzvah. The Rashba further explains that the reason one who converses in between sections of the Megillah reading is chastised is because once the bracha has been recited one should maintain his attention to the fulfillment of the mitzvah.

A relatively short break in the Megillah reading – for example to do an introduction to the particular chapter, even with a short skit or song – would not be forbidden, because people’s intention is still on the reading of the Megillah.

But a lengthy break, to do an entire Purimshpiel, would be problematic, because with such a long break, people’s attention will surely wander from the fulfillment of the mitzvah of the Megillah reading, thereby introducing a break between the reciting of the bracha and the fulfillment of the mitzvah. Considering that after the Purimshpiel, people will naturally want to take a break, congratulate the performers, some people will leave, it would certainly result in a violation of the principle that one’s attention should remain focused on the fulfillment of the mitzvah.

Furthermore, to interrupt the Megillah reading in a fashion that would make it very easy for people to walk out en masse before the completion of the reading would be a violation of the principle of lifnei iver lo titein michshol, not to put a stumbling block before the blind, because the mitzvah is to hear the recitation of the Megillah—the mitzvah is not related to hearing the performance of the Purimshpiel. And this is especially applicable in this case, since even children are obligated to hear the recitation of the Megillah (OH 689:1).

Therefore, it is not permissible to interrupt the Megillah reading to do an entire lengthy Purimshpiel which would cause people to intentionally miss the completion of the Megillah reading. Other things should be done to try and accommodate the concerns, such as starting earlier, reading faster, or otherwise attempting to complete the evening in a timely fashion.