Hugh Hefner & Crystal Harris: No Gifts Please!

It's just a few weeks until Hugh Hefner and Crystal Harris tie the knot -- all the details are set, and the wedding invitations have been sent out.

But rather than heading to Bed Bath and Beyond to create a registry, the couple has asked their 300 guests to make donations to select charities in lieu of gifts.

"It was actually Crystal's suggestion and I thought it was a great idea," the Playboy founder tells Us Weekly. "The point of it is, we don't need gifts. A lot of people are in need and the notion of giving to charity instead of giving gifts to us just made sense."

The charities that Hefner, 85, and Harris, 24, chose include Children of the Night, an L.A.-based foundation that's dedicated to ending child prostitution; charity: water, a non-profit that aims to provide clean and safe drinking water to people in developing nations; and St. Jude Children's Research Hospital. "No child is denied treatment, and it's a wonderful organization," Hefner adds.

The bride- and groom-to-be are "expecting a full house" for their wedding, due to take place at the (where else?) the Playboy mansion in L.A. on June 18. As for wedding-day jitters, Hefner jokes, "We’re waiting for responses to our invitations. If we don’t get enough responses, we won’t get married!"

But The Girls Next Door star is "very excited" about the big day. "Crystal is wonderful and she's done a really terrific job so far with all the planning. She is the one for me!"

Credit: Us Magazine

Hugh Hefner & Crystal Harris' Wedding Invitation

It's getting down to the wire for Hugh Hefner and his fiancée Crystal Harris, who will wed on June 18 at the Playboy Mansion.

The Playboy founder, 85, announced on Tuesday that his and Harris's wedding invitations have gone out, and friends and family have already started receiving them.

"Crystal Harris and Hugh M. Hefner request the pleasure of your company at the celebration of their marriage," the invite that Hefner Tweeted read.

And when it came to how the invitations would look, Harris took the reins.

"Crystal pretty much designed the invitations the way that she likes it," Playboy publicist Kellie Olisky tells PEOPLE. "She had this idea and we found this company who will help us out and they have been great. Papeterie is custom-making everything. Hef picked the paper; Crystal picked the colors."

Although the invite appears to look relatively simple, it's part of the bigger event.

"We have added little fuchsia and turquoise Swarovski crystals on the invitations, which are really pretty," Harris, 25, told PEOPLE. "And we are going to have fuchsia and turquoise flowers at the wedding, so it will all come together really nicely."

Credit: PEOPLE (Dhavi Shira & Cynthia Wang)