This would be the 'fun' part. He had barely ensured that would reach his father about what he'd volunteered himself for, the quest he'd undertaken. And he knew that he'd be very displeased to hear about it.

"I must tell you something that you will not wish to hear."

That's as close as he's getting to saying: brace yourself and please don't yell at me.

"While in Rivendell, I represented our realm in a council. Details of it I am not sure I should say," Even if details will reach him regardless. "but I offered my skills in the protection of another. Our path took over over Caradhras but we could not traverse it safely. Gandalf chose to take us through Moria as an alternative."