07/12/2011 at 02:20 PM EDT
The weeks leading up to the birth of baby
Harper Seven were busy for Victoria Beckham
. Really busy.
She's unveiling a new collection
in September and raising three boys – not to mention all those new pink duds
she had to find space for.
"She was saying, 'I just want her to get here and want to be holding her in my arms – not in my belly,' " a source close to Beckham, 37, tells PEOPLE. "She had not been all that tired until the end, when it is just so hard to be active so pregnant."
Fast-forward to July 10, when Beckham and husband David Beckham
, 36, welcomed newborn daughter Harper Seven Beckham
, and it looks like all the hard work paid off.
"She was so excited and really just ready for the baby," the source adds. "She [had] been working really hard to get as much done as possible before Harper's arrival. She was unsure of how she would manage time and schedule after [Harper] arrived."
Like any seasoned mommy, Beckham had her nursery in tip-top shape "for weeks" prior to Harper's arrival, the source says. But even with all the advance planning and help from her husband, who kept tabs on the all-boys brood – Brooklyn, 12, Romeo, 8½, Cruz, 6½ – it was "a crazy explosion keeping all their schedules together."
"David was, of course, over the moon about her arrival," the source continues. "He was around town taking the boys to and from camp and to their soccer lessons – all the stuff he usually shared with Victoria."
So how did the kids pitch in? "The boys, who are all so sweet and a really caring and very well-mannered bunch, are all old enough to really know what was about to happen," the source says. "The kids seemed happy but they are such boys. [It] will be interesting to see how they take care of their little sister."
The Beckhams, who were joined by some of Victoria's family from the U.K. for Harper's arrival, are spending their first full-time summer in L.A.