I wouldn't worry about the trail up to Margaret Lake. I've only done it in winter, but it should be just fine in summer too. It's actually the first trail I ever did, by myself (not something I would ever recommend or do now that I know better and realize why), which speaks volumes for the trail's gentle nature. A good beginner's trail. That being said,
please respect and don't underestimate the trail. To echo Blair, there is potential for a lot of expensive damage to our rigs, and as some people have experienced first hand, potential for damage to ourselves. That's why larger groups can be a great asset. But you have to learn somehow, so good on you for wanting to try. Too bad about missing the 101.
Please also make sure you have the right recovery gear, including tow straps and
proper tow points, ect. If you're looking to get stuck, I hope you have your own winch, especially the larger vehicle, as it's unfair to ask/expect someone else to burnout or wreck thier own rig/equipment to rescue you because you're unprepared - I actually was in possession of my winch before my Jeep. Otherwise, start small and build your confidence/experience up while building up your arsenal of off-road goodies. There's a lot of experience on this site, so please ask if you have any questions.
Remember: Respect the trails and they'll love you back. Have a great time out there