The wedding will be set in the gardens of the couple's Bel Air mansion and Jen has hired friend and wedding planner, Kevin Lee, to help her sort out the details.
A friend of Jen's told us: "She's got an amazing plateau-like area in the back that faces the west, so think 'sunset wedding'.
"Jen will wear two dresses on the day – one for the wedding and one for the reception. She'll go bolder with Valentino for the nuptials, and classy and clingy in Lanvin for the reception."
And according to our insider, although Jen has got two movies in the pipeline, she will clear her schedule as soon as she can to make way for babies.
Justin's rep excitedly confirmed the engagement last week, telling America's People magazine: "Justin had an amazing birthday on Friday, receiving an extraordinary gift when his girlfriend Jennifer Aniston accepted his proposal of marriage."
Read more details about the ring, dress, venue, guests and babies only in this week's Reveal magazine.
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