"Contained wackiness" sums up this episode pretty well. The storyline sort of jumped all over the place, but it did progress in a logical fashion that kept the main themes of the episode in check for the most part. I did think it took awhile to really find its actual POINT--by the end of the second act, all that's really happened is Bart found a cellphone and caused a lot of mischief with it.
I really like the theme of when a parent should let their kid go out and explore the world, but an excellent idea was poorly handled in this episode. If it was a recurring theme throughout the episode instead of just the third act, it would've had more impact when Bart ran back and clung onto Marge's leg at the end. As is, it's 15 minutes of silly adventures and 7 minutes of a solid theme that doesn't get enough time.
I liked Marge's characterization, and Bart was handled pretty well too. I found it odd that Homer didn't show up until about halfway through the show. The gags were kind of a weak point for the episode--none of them were terrible, but it had all felt pretty stale and basic. Even some of the prank calls felt like a stretch this time (and one reminded me of Maya Buttreeks). A few scenes stood out for me, like the fun construction site gag and the quick visual jokes of the day/night sequence, but most of the lines were standard fare and failed to impress.
Execution-wise, just sort of the typical Jean episode. And like Jean episodes, it has one or two visually impressive/creative moments (in this case, Marge's Machu Picchu sequence) and one or two lame music montages. It's not bad, just...stagnant.