Okay, now if this were my family, I would do the following:

1. Folk-process the words (which may not be remembered correctly) to make them more rhythmic. See below.

2. If the friend remembers the tune, all well and good. Assign chords to it, and have someone who plays guitar accompany it. (Everybody knows SOMEBODY who plays guitar.)

3. If the tune is lost, make up another one.

4. At the funeral, sing the song once, extemporize upon the chords for an interlude, then sing it again.

Seagull, seagull fly o'er the sea.
Seagull, take a message for me.
If you see a big ship sailing on the foam,
please tell my daddy
his little laddy
waits for him at home.
Seagull seagull fly o'er the sea.
Seagull, take a message for me.

That will make it longer and more formal, so as to fit better at a funeral.