Oh, also if a more traditional or formal funeral with prayers, etc. The priest or funeral chapel will have ways of dealing with these types of matters. There may be some negotiation, but often the OP will be placed back a few pews or the exs will be separated by the aisle.

There can be many different options to help everyone come together. Speak to exH when it comes up and otherwise find out where the service is and speak directly to the priest or those company handling the funeral.