In these type situations it's important to expand the penalty options explanation to include the timing ramifications, such as, "if you accept the penalty, the clock will start on the RFP and if they fail to get a play off before time expires, they will be entitled to an untimed down. If you decline the penalty, the clock starts on the RFP and if they fail to get a play off before time expires, the period is over". I would make sure Captains of both teams understand that.