Does she mean dwarf Orange Trees, I would have thought them to big. Or Does she mean Kumquat ?

Be aware that government agricultural regulations may not allow trees to be shipped depending on location of seller and buyer. You did not state your locale on your profile so be aware that an international citrus tree shipment most likely would be prohibited. In general the bountiful tree you daughter envisions will not have the same appearance it did prior to shipment nor the same
fruit count remaining on the tree. There are many other difficulties with this idea too numerous to mention unless the wedding was being held somewhere along the mediterranean coast of Europe.

If you will allow me to suggest an alternative which would be a compromise. This would be a silk miniature orange tree centerpiece on the table. At each table underneath of
one of the chairs would be a sticker label of orange color.
At the end of the festivities the guests would be
instructed to look underneath their chairs. The one sitting
on that chair gets the beautiful silk miniature orange
tree which can be used as decor in any room of ones
home sun or no sun.
The orange sticker arrangement will prevent resentment
among the guests since this would be a random affair and
impartial.

I wish your daughter and her fiancé everlasting happiness and I give you my Best Regards: Eclectic

I believe that you will be able to purchase some dwarf orange trees which are in fruit from a good garden centre on or about the time you have stated. The only thing you need to think about is, that after the wedding they will suffer from spider mite and milldrew when kept indoors. They can be difficult to keep the light and moisture levels correct and are apt to lose their leaves. I would recommend that you look for other centrepieces rather than orange trees. Also seeing that you intend to buy several, you need to consider the expense as they are not cheap.The only good thing about the trees is the heavenly perfume of the flowers.