Did this ride with Mrs Ononeorange last month. Awesome. Definitely go from Victoria Bridge, as it descends far more that way. It’s a great easy track to begin with (we cut up through the first on the main track and then dropped through the farm to the first river crossing). After the loch, it’s a long but gradual pullup, then once over the top it becomes more technical for a while – although the trickiest bits can be walked.
After the lodge it’s an easy track again, along Loch Etive, although if they’re tired by then it’s very undulating for the last 5 miles (to a Southerner, anyway!).
We met a school party of I suppose early teens with teachers, they were tackling the other (hard) way, yours should be fine, it’s a big day but absolutely stunning. Recommended! Enjoy.