I'm late to the discussion, but to add my own .0000019 cent's worth...
Is Disney having a series of interstitial shorts of the Muppets on Disney Junior a good thing? Who knows at this point? It's hard to tell.
Is it good that Disney is looking for ways to utilize the Muppets and get more out of them? Absolutely! This is the most Disney has ever done with the Muppets since they purchased the franchise a decade ago! Between 2004 and 2011, Disney has shelved more Muppet projects and broken more promises than they did actually coming out with new things (which during that time only included MWoO and LTS).
Is this what Jim would have wanted? Why not? Let's take a step back for a moment and look at Jim's career over the years: when he started the Muppets in 1955, he wasn't really serious about making a career for himself in puppetry, he just got into it as a way of getting into the television business, which is where he wanted to be. Did he want the Muppets to be main source of recognition? Not necessarily. Throughout the 60s, he tried various different projects to show he could do more than just puppets, including such experimental films as TIMEPIECE, YOUTH '68, and THE CUBE - all of which may have been personal successes for Jim, but they each pretty much had mixed reaction from the public at best. It really wasn't he finally accepted the fact that the Muppets are pretty much what he's known for that he began to emerse himself more into the art of puppetry and as a result, we got such treasures as TMS, TMM, GMC, MTM, DC, LABYRINTH, among other things. On that same token, did Jim want the Muppets to be regarded as kiddy fare? No, you're right, he didn't; already, puppets had a stigma of being kiddy entertainment, and he tried hard to prove to people that puppets aren't just for kids, and as such, he didn't want to be labeled as a children's entertainer - he even had a mild little fit with Joan Ganz Cooney at one point in the 70s, saying SST's success ruined his life, though he assured him the exposure he's gotten is exactly what he needs, and the profits from the merchandising would also help further fund his other projects that he wanted to get off the ground. Again, the way Jim finally came to terms with the Muppets being what he was mostly known for, he eventually accepted the fact that although he tried hard to prove puppets aren't just for kids, kids were one of his biggest audiences, and as such, he began to work on more and more projects that were aimed specifically at children, such as FR, MB, and as pointed out, those Play-Along videos.
So, would Jim be upset with how Disney is utilizing the Muppets at this point? I'd say probably not; after all, his initial of selling the Muppets to Disney before he died was so that the Muppets would be with a company that would ensure they would be kept alive for generations to come, like Disney had already been doing with Mickey, Donald, Goofy, et al. after Walt's death.