Few things can be more terrifying than an out-of-control mob at a rock concert — especially when that mob hasn’t had a nap.

Chris Wiser of kiddie-rock duo the Sugar Free Allstars nearly shudders at the memory of one such show, when he and his fellow Allstar, Rob Martin, faced a crowd of unruly children at a Del City library.

“There was one year that the kids really couldn’t hear well. They were already up dancing, and I was trying to put out fires where kids were getting a bit overly rambunctious,” said Wiser, 42. “I lost control and it was … pretty terrifying.”

That remembrance is among the reasons the pair, among the country’s top recording artists of kid-friendly rock ’n’ roll, keeps its live shows fast and lively, with nary a moment of downtime for pint-sized concertgoers.

“It’s scary to think, ‘What if we slow it down and we lose control and can never get it back?’ ‘Cause that’s happened,” Wiser said. “With the shows we do now, it’s just no dead time. If we’re not playing a song, we’re talking and moving back and forth. We try to make sure there’s some kind of audience participation in everything.”

Fortunately for the Allstars and their fans of all ages, the act appears to be keeping plenty of people happy. The Allstars’ new album, All on a Sunday Afternoon, has won significant play on SiriusXM Radio’s Kids Place Live channel, particularly the gospel-tinged first single, “99 Questions,” in which Wiser rattles through a litany of queries (“When I grow up like you will I have to wear my shoes?”) for listeners to ask Mom.

That’s atop other recent successes, including contributing a song to the compilation CD All About Bullies ... Big and Small, which earned a 2011 Grammy for Best Children’s Album.

And it’s happened without the Oklahoma City-based guys having to transform themselves from the days when they were playing music clubs for grown-ups.

“Musically, we didn’t really change anything,” Wiser said. “Subject matter-wise, it’s not necessarily that we think about a kids’ song; we just basically keep it all-ages friendly. We didn’t dumb anything down. When people ask, ‘What do you think about when you’re writing a song for a kid?,’ we say, ‘Well, we’re thinking about writing a song.’” For their latest effort, the Allstars thought about tackling that tried-and-true staple of rock: the concept album.

“It just so happened that some of these songs we had could kind of fit under this umbrella of things you might do on a Sunday afternoon,” said Wiser.

The resulting disc swings from the brisk stomp of “Gotta Get Up” to the spot-on Philly soul of “Ready to Give Up Teddy.”

And that’s partly the group’s mission: to introduce young listeners to the funk, soul and R&B that formed the soundtrack to the twosome’s own upbringing.

“Maybe part of the reason so much of popular music is pretty bad is people don’t have a solid base of good music they’ve heard in their formative years,” Wiser said. “If you’re used to bad music, at a certain point in your life, that’s what you expect. Our goal is to hopefully encourage a more discerning consumer of music.”

From Seinfeld to ukulele

Seinfeld fans know Heidi Swedberg as Susan Ross, George Costanza’s ill-fated fiancée. But the actress’ first love is the ukulele, an instrument she began playing during her childhood in Hawaii.

“You can’t be born in Hawaii and not feel a special affinity for the culture. It is so rich,” Swedberg said. “My sisters and I all received our first ukuleles from the Easter Bunny in 1971, when I was 5 years old.”

As for being known as Susan, the woman who had the misfortune of dying by licking toxic weddinginvitation envelopes — Swedberg said she loves it.

“I love that people feel familiar with me,” she said. “I feel privileged to have been introduced to so many people, and I really enjoy turning the tables and becoming acquainted with them.”

Swedberg does that through constant touring and gigs nationwide — like supporting the Sugar Free Allstars on Sunday — with her Sukey Jump Band.

“It really is an all-ages experience. We love to share music making and encourage participation, but never put anyone on the spot,” she said. “We love to make things up, remain fluid, perform and have a great time.”