I won't pretend to even suggest how you can work this out with your wife - that is for the two of you to solve. However, I can tell you frankly that children sleeping in their own beds is not a developmentally-based accomplishment. Otherwise, all children would have been sleeping in the same bed with their parents for a time, and this
simplySimply sleep does not occur with most children.
Parents setting limits with children (and in your wife's case, with herself) is an important skill. She should ask herself whose needs are being met by having the kids sleep in your bed. It's entirely possible she's unwittingly paying more attention to her needs than to the needs of the kids. If the two of you really want the kids to be sleeping in their own beds, you'll get it done. Be decisive, and don't expect the kids to make this easy for you.