Although I do sympathize these people are going through a ton of stress right now , I couldn't imagine, however....keep in mind, your time is important. I would address the situation with them and give them a few options. Let them know you are so sorry for their situation and sympathize completely but the encroachment on your time IS becoming a bit of an issue and you would like to work with them on solving it. You could offer to take the kids longer, WITH an extra charge.
You could ask them if they could leave work a little early to pick up on time, given the extra commute required. You could ask if there is friend or family to help out by picking up on time so you can have your personal time. Always put your self in someone elses shoes before talking, (keeps us all humbled,acknowledgin g others troubles) on the very same note, keep your needs in mind also..kindly sympathize but let them know your time is important. Good Luck....and prayers for them..(couldn't imagine what it's like to loose your home)