Britney cleans up nicely but is still stuck on a dirty habit; plus, Jessica gets booed, Lindsay stays glued to Samantha, Jennifer & John rendezvous, Miley, Demi & Ashton do good and more ...

The campaign to prove that Britney Spears is back on track -- last week her lawyer called her progress "astonishing" -- has been humming right along in recent months, but did it just hit a bit of a speed bump?

On Friday, paparazzi snapped the custody-settling-but-still-closely-supervised popster puffing on a cigarette as her nearly 3-year-old son Sean Preston stood nearby, alternately eyeballing his bikini-clad mom and curiously checking out her lighter and pack of Marlboro Lights.

(See more of Sean with the cigarettes and lighter here and here.)

Jenny, Jim and Brit at Generation Rescue's fundraiser in Los Angeles on July 19

At least this seeming setback is slightly tempered by Brit's successful outing Saturday night to a fundraiser for Generation Rescue, an autism research organization fronted by Jenny McCarthy, whose son was diagnosed with the condition.

"She looked great and seemed really happy," an eyewitness tells People, with another insider adding to Us that she was "smiling a lot."

The vodka company-sponsored shindig took place at the Los Angeles home McCarthy shares with boyfriend Jim Carrey, and they made a point of posing with their PR-generating guest, who was sporting an occasion-appropriate black dress, surprisingly cute shoes and her still relatively fresh-looking stick-straight extensions.

Us says Britney sipped red wine, while People reports she never strayed far from her assistant Brett and nixed small talk with the other guests, including fellow custody-battle veteran Charlie Sheen (there with wife Brooke Mueller) and a "lovey-dovey" Rose McGowan and Robert Rodriguez (so much for those breakup reports).

"She smiled and clapped during the video about autism," relays the People mole. "She was very into the information and watched a little bit of the dancers from 'Dancing With the Stars,' sneaking out during one of the performances."

While Spears' understandable exit during the 'DwtS' interlude gives us some hope in her fitness to make her own decisions, her apparent inability to curb her cancer stick addiction while in the presence of developing lungs is less reassuring.

In the snaps, the impressively hard-bodied Brit is seen smoking just a few feet away from Sean on the patio of her Beverly Hills home.

The mischievous tyke is captured flipping the top of the cigarette package and playing with a pink lighter, although photo agency X17 says Spears actually used his inquisitiveness as an opportunity to teach her oldest not to touch mommy's nicotine delivery system.

And in Spears' defense, she does appear to be motioning for him to put the cigarettes down and reaching to take them away.

Still, Brit's prior quality time with a court-appointed monitor probably should have covered such common-sense issues as the potential dangers of secondhand smoke and how to keep hazardous objects out of the reach of little hands (there are no fewer than three lighters and two packs of matches sitting in a bowl directly in front of Sean).

On the plus side, Spears, who is rumored to be working on a new album for release at the end of the year, was also photographed toting and planting kisses on Jayden James, who turns 2 in September.

Spears' smoke break comes just days after she agreed to give sole custody of her sons to ex-husband Kevin Federline.

People says that as part of the agreement, she'll bump up monthly child-support payments to the image-rehabbed K-Fed from $15,000 to $20,000. In addition, his cucumber-cool attorney, Mark Vincent Kaplan, is said to have asked for and received $250,000 for his hard work.

Britney will reportedly be granted three visits per week with Sean and Jayden, along with two overnights, up from the current two weekly visits and one overnight.

"All Britney was seeking was a formalization of her increased visitation that she's obtained over recent weeks, and the additional overnight," an insider tells the mag. "She won both of those requests."