You could tell everyone that he's spending a year dead for tax purposes, like Hotblack

You can read the bit about Saint Antwelm (the king who believed that what people really want is a good party, willed his fortune to that, and was canonized for it)

Personally, I like the bit about Arthur making sandwiches - I think it speaks to the joys of a simple life

If I were you, I'd slap a hot pink somebody else's problem field on top of the coffin and then have a funny speech with quotes to explain it. (They sell bright pink sequined duvet covers for little kids that aren't too expensive)

You could give the eulogy in your bathrobe (ideally with a bone in your beard)

If your dad drank or partied, can you serve gin and tonics (or pan galactic gargleblasters) during the eulogy? My dad died this year, and he drank a lot and dislked religion, so I served booze during the eulogy and played the parting glass in lieu of prayers or a hymn

End with So long and thanks for all the fish

And I'm sorry about your dad and proud of you for sending him off with a laugh - I think that hoopy frood would be proud of you too