Part of the society and manners of the time, with which I have always had trouble, is the paying of visits, and the obligation of calls. I think Edward Ferrars visiting the Dashwood's cottage falls under that umbrella, though.

If one wants to keep the general respect of one's acquaintance, one visits. In addition, if one wants to indicate esteem, or liking, one goes to some little trouble to pay calls. If one does NOT, that sends a message.

Mrs. Dashwood expressly invited Edward Ferrars, and he genuinely likes and admires the family. He probably always intended to call on the cottage, and simply had to arrange the time and situation to do it.

In addition, he has a secret engagement to Lucy. He does not WANT to visit her, the way he wants to visit Elinor and her family, but if he goes to one, it would be a sign that he COULD HAVE gone to the other, had he a mind to. So, Edward's dilemma is how to manage all this social juggling, without making his family outraged at his visiting the Dashwood women, nor making Lousy (sorry, Lucy) think she was supplanted.

He manages it the way the novel paints it: he is ostentatiously going to visit Mr. Pratt's, perhaps for a fortnight or so. Lucy is there, and he tells her that he is going to call on the Dashwood's cottage when he leaves -- but only for a week. Lucy gets twice the time that the Dashwoods get, and Edward, who has been absent from Norland for a month, can truthfully say that he was at Mr. Pratt's for about a fortnight, leaving vague which fortnight was the time of his visit.

I do not think he was thinking in terms of what part of the 'holiday' would cause him what kind of pain. It was mere politeness, wrapped inside the awkwardness of his situation, and friendship, which he is trying to convince himself to feel for Elinor, that makes the whole plan take shape the way it is.