Jamie Lynn Spears Spends B-Day Shopping at Wal-Mart

Jamie Lynn Spears celebrated her 17th birthday with fiancé Casey Aldridge shopping at Wal-Mart and having dinner at Ruby Tuesday, People says.

Really. Which is great. In fact, we support whatever makes America's favorite unwed teen mom-to-be and teen baby-daddy happy.

"They both seemed really happy, both in really good moods," a source tells People of the couple's outing near Aldridge's home in Liberty, Miss.

"Jamie Lynn had a big smile on her face."

With Wal-Mart purchases in hand, Spears, who is pregnant with Aldridge's child, took in a quiet dinner with Casey, 18, at the restaurant.

"It was just the two of them," says the source.

"They were like a little adult couple, very low-key."

Jamie Lynn Spears recently has been flashing a big engagement ring from Casey Aldridge. They are expecting their baby this summer.

Meanwhile in Los Angeles, Jamie Lynn's big sis Britney Spears gathered with the rest of the Spears clan for a family dinner in Los Angeles.

Britney, parents Lynne and Jamie and brother Bryan Spears joined a group of about 10 people for an Italian feast at Ristorante Peppone in Brentwood.

"[Britney Spears] was in a great mood, and had dinner with her family and friends," a restaurant source says.