As this is a connection and thus all on one connection, AC is well aware that your parents are inbound and will almost certainly misconnect.
Before calling AC, pull up your parents' PNR online and see whether AC has already rebooked them. It is fine to call AC and ask, but it is very risky for more than one person to be working on a ticket at once. If someone at AC is doing so and you then start a separate process,the risk of unticketed reservations arises and that is a mess, particularly for travelers who really need to keep this simple.
If not already in the PNR, you might also ask AC to include a note listing the specific languages which your parents speak as well as your mobile number.
As there are no later flights to IAH, your parents are almost certainly overnighting at YYZ. Once they have a hotel voucher, you might consider calling the property directly and providing your mobile number so that you can facilitate communications.