A memorial ceremony is simply a funeral without the coffin or ashes being present.
Perhaps the ashes are to be scattered later and/or in a private ceremony.

They are still an effective way to say goodbye to a loved one.

The ceremony may take place in a private house or garden, a local village hall or perhaps in a hired function room in a hotel.
The latter will usually be able to supply refreshments / drinks / meals afterwards.

The service can be of whatever duration you feel is necessary. I suggest that a maximum of 1.5 hours is planned for, and if it finishes sometime after an hour, then nothing is rushed but hopefully that is sufficient time to have marked and respected the person’s life.

Another tip is to start the ceremony at 11am, which allows time for mourners to travel, then ends comfortably around lunchtime. But this aspect of the planning is entirely your decision.

A funeral director is not usually involved at a memorial ceremony, so I charge a higher fee than for cremations or burials.