How will your ex wife feel about seeing you two be intimate? For some this would be a fucking dagger in the soul. For others, could be hot. For others, indifferent.

Do you and you ex wife sleep in the same room? Will you and your girlfriend?

If the space is adequate, doesn’t involve a big physical relocation for your ex wife, the house is yours alone, the kids are old enough to understand, and you plan on all being respecful, the yeah, it can work.

That’s a bunch of ifs. Not all are in your control. Any are not met and you are the asshole.

If say it’s dicey.