It is interesting how Charles and Mary make their separate cases for not staying with little Charles in order that they may go to dinner and meet Capt. Wentworth, but citing the same reason: they can be of no use, because they are parents.

Charles: "what was there for a father to do? This was quite a female case, and it would be highly absurd in him, who could be of no use at home, to shut himself up."

Mary: " I am of no use at home -- am I? and it only harasses me. You, who have not a mother's feelings, are a great deal the properest person." (ch. 7)

What convoluted logic they both use in order to excuse themselves and do what they want to. It's funny and sad both. But, Mary has the best line in this argument:

" If there is any thing disagreeable going on, men are always sure to get out of it"