|Jessica Alba and Justin Timberlake|
A source told People magazine: "Justin and Jessica are planning a big summer wedding.
"Jessica initially wanted a smaller, more intimate wedding, but Justin from the beginning wanted a big wedding and that's what they have decided on."
Jessica has yet to decide on her dress but is "very involved" in planning the ceremony, with the source revealing the couple plan to "include all their friends".
The insider added: "Justin has promised her the best day ever."
While Jessica - who split from Justin last year only for them to rekindle their romance before the 'Social Network' star popped the question - hasn't yet found her dress, it was recently claimed she already knows who she wants to design her gown.
A source said: "Monique Lhuillier has sent over some sketches. She's Jessica's first choice."
And the pair are said to be getting a lot of help with planning their big day from Justin's mother, Lynn Harless.
The source said: "She's helping with every little thing."