As a very frequent border crosser and having family members that cross daily here are a few tips/guidelines for your trip.
1. Make sure you have notarized travel documents for each Scout you are bringing with you across the border. These include a permission to travel abroad with a list of specific adults on specific dates. Permission to obtain emergency medical care for each member (youth and adult) while in Canada if needed. Create a travel packet for each member. A gallon Ziploc bag that contains notarized forms, passport/border cards/enhanced state ID/original raised seal birth certificate, troop permission slip, and a copy of the member's health form.
2. Packets accompany the members and are held by the driver of each vehicle. Driver hands the packets to Canadian/US customs agent at the border. Identification document on top, notarized permission to travel abroad form next, then notarized emergency health and regular health forms round out the bundle. Driver's packet is first. Organize packets by front seat, middle row and back row of the vehicle, driver to passenger sides. This is how we have done it for 25 years with our Girl Scout troop when we travel to Canada each Mother's Day weekend for a big camporee near London Ontario. Never had a problem crossing either way.
3. All phones/electronics turned off and stowed at the time of crossing. No sunglasses or hats on. If your driver wears prescription glasses have them switch temporarily to indoor glasses from their sunglasses. Border agents don't like sunglasses. Or they can take the glasses off for discussion with the agent.
4. No cameras at either border or near the border area. NO PICTURES OF BORDER AGENTS OR SURROUNDINGS.
5. Keep all vehicles in the same lane and together so that everyone deals with the same agent. Trailer comes through last. Designate a meeting spot after clearing customs. DO NOT gather the convoy on border crossing property. That way you will be close if there is a problem but not interfering with traffic flow. Everyone should be organized the same way going on to the border zone property too.
6. Parents and their kids should be in the same vehicles at the time of border crossings. As should siblings. You can regroup before entering or after exiting the border zone if siblings don't want to travel together. NEVER, EVER REGROUP IN THE BORDER ZONE.
7. NO WEAPONS, MACE, PEPPER SPRAY, NOTHING BIGGER THAN A POCKET KNIFE in vehicles or on person. CANADA DOESN'T DO GUNS!!!!!! Make sure all guns and ammunition are left at home. You will go to jail and they will seize your vehicle forever if you bring a gun in. Larger cooking knives need to be secured in a patrol box in a trailer or trunk. Pocket knives put away pockets or backpacks.
8. Proper current identification for everyone. Passports, passport cards (obtained just like a regular passport with the same forms and processes, only good for land crossing to US/Canada/Mexico), enhanced state ID (similar process to getting passport but done at your state DMV office, not available in all states). Our group and several school groups here also use raised seal/original birth certificates for youth under 18. There has always been an exemption for organized youth groups traveling between Canada/US to travel on birth certificates. Anyone over 18 has to have a passport/passport card/enhanced state ID. Check guidelines before travel.
9. Turn off data usage and roaming services for mobile devices unless the device has an international usage plan. It isn't uncommon for people to rack up hundreds if not thousands of dollars of roaming/international usage charges. A quick text can cost $5 or an email check can cost $25 or more if you don't have an international plan. My daughter tallied up $550 in 2 days because her phone didn't connect properly to the hotel wifi. Phone company was good about it, but they didn't have to be. Just turn the devices off. One leader can get a temporary international plan for a month and roll the cost of that into trip costs. We are doing that when the girls go to England in August.
Hope this helps. I have been crossing the border for over 50 years, and 7 years with Girl Scouts and never had a major problem. A few crabby agents here and there, only 2-3 vehicle searches. Searches were because my vehicle matched a vehicle of interest (Amber alert type things). Follow the Scout law and you shouldn't have a problem. Courteous, kind, obedient, friendly, cheerful and most of all Be Preapred. Nothing worse than rifling for documents at the agents shack.
Have a great trip.