In that exercise there is one sentence whose English doesn't quite jibe with me:
-- The kids finished the ones we'd brought.
I don't think the use of past perfect tense here corresponds to what you would actually use in English. You'd be more likely to hear:
-- The kids finished the ones we brought.
But I realize that in French you would actually use le plus-que-parfait:
-- Les enfants ont finis celles que nous avions emportées.
As it stands, the English sounds a bit off but it gives a strong hint as to which tense to use in the French version. Still, I would use imperfect in English and, if necessary, provide a hint for the French.
What do the professionals think?