You can't is the simple answer.
How many km since the vehicle was serviced? If I has been more than 100km, they should have told you (the don't usually, but should) to recheck the torque on the wheel nuts after 100km. Depending on wheel, climate and condition of wheel nuts/studs, they can backoff within the first little bit.
Wheels about to fall off generally make quite a racket before they fail completely. Did you not notice any symptoms?
Based on Canadian law, unless anyone was actually physically injured, you cannot go after anyone for damages. You are fully within your rights to attempt to recover costs for the damages to the vehicle as a result of the accident. A court of law will decide who is responsibility and I. What capacity you will be compensated.
I am sorry to hear that you and your family were put in Harms way.