Jamie Lynn SpearsJamie Lynn Spears may have other things to think about over the next few months - as she gives birth to her first child in the early summer - but plans for her wedding are reportedly under way too.

The Zoey 101 star, who turns 17 today, is said to have only got engaged to dad-to-be Casey Aldridge last month but a source told In Touch Weekly that mum Lynne Spears is already working on the couple’s pre-nupital agreement: “The contract is already drawn up and ready to go. Lynne’s not sure marriage is a good idea, but she’ll go along with that if that’s what Jamie Lynn wants, as long as Casey signs the contract.”

“Lynne is keeping an eye on him. He doesn’t seem as committed to the relationship as Jamie Lynn.”

Meanwhile Jamie Lynn is said to be making plans for the ceremony itself and hopes to hold the event at the family’s estate, named Serenity, in Kentwood, Louisiana: “Jamie Lynn is planning to have the baby at Serenity, and, soon after, she will also get married there.”

“[She] wants to wait at least several months to get her figure back so she can wear a beautiful wedding gown and then have her dream wedding.”

And big sister Britney Spears will play a key role in the proceedings: “She wants Britney to head up her bridal party.”

Britney was spotted shopping for a birthday present for her sibling in Los Angeles yesterday.

She was spotted “in good spirits” at the Ed Hardy boutique in the Beverly Center as designer Christian Audigier showed her around the new spring collection.

A spokesperson for the store explained: “Christian and she were laughing as she tried on Ed Hardy sunglasses and checked out the bathing suits.”

Britney is said to have picked out a selection of handbags, scarves and t-shirts for her sister as well as a pink Ed Hardy shirt. She is also said to have picked out items as gifts for her conservator dad Jamie Spears.