The 33-year-old singer has been planning her special day and she wants lots of people to be present at the lavish ceremony to witness her and Johnson tying the knot, reported Contactmusic.
"I've been very picky on how I want everything to look and feel. Eric's family alone is almost 90 people, so it'll definitely be a big event," Simpson said.
The blonde beauty, who has daughter Maxwell, two, and ten-month-old son Ace with Johnson, has remained tight-lipped about the date of their nuptials.
"We are very close to sending out our invites," she said.
Simpson was previously married to Nick Lachey, 40, in 2002 and they divorced in 2006.