What do the children decide to do when they return and the house is blown up? What reasons inform their decision?

The kids decide they have no choice but to search the loops until they find Miss Avocet. THey need to find her. Emma locates something called the Map of Days, which is labeled with every loop ever known to exist. Millard explains to Jacob a concept called leapfrogging, where you travel to a loop and then have access to all other loops that existed at that time, even if they have ceased to exist in the present day. Through this method, you can travel through time. They are worried that the wights have taken the ymbrynes leapfrogging to a place that existed in the past, so they not only have to figure out where they are, but when too.