There is a subtle point which was part of that that was not mentioned explicitly, that I probably should have. The adventuring proficiency is worth 4 general proficiencies, so…
This halfling proficiency costs 2, but “normal” adventurers get one plus adventuring. To take the 2 point proficiency, you give up adventuring for a total of 5 proficiencies at first level. Two go to halfling and you have 3 general proficiencies left over, which should compensate for the loss of adventuring.
I would have these drop away as the halfling advances, so 3 at level 1, 3 at lvl 2, 2 at level 3, 1 at level 4, adventuring at level 5. This is a slightly modified version of how normal men do this when brought into the adventuring life, and gives them the can’t go home again feeling.