I wonder if the present conditional is the correct verb tense for my sentence. If it is, is it better to express the word would or could? If it is not, what verb tense should I use?
For example, your parents could allow you to have 3 / 4 hours of leisure time to meet your friends as soon as your school day is over, and then you could / would / other option do your homework.
As you probably are aware, modal verbs in English like "could" and "would" can often cover a wide variety of meanings and are sometimes ambiguous even for native speakers. The ambiguity, however, is almost always resolved by the situation or is not important to the overall message.
If you say: "then you could do your homework," you mean then you would be able to do it or then it would be possible to do it or then you would be allowed to do it. If you say: "then you would do your homework," you mean "under that prior condition you would then go on to do your homework as expected" or "then you would do your homework if you actually felt there was a need to do so."
You could also use "might," but this would suggest that doing homework was not a strong probability.
The origin of "could" is a past indicative or past subjunctive form of "can." It also doubles as the conditional form of "can" and so can include any meaning "can" has (e.g., to be able, to be permitted, to be possible, etc.) The word "would" creates the conditional form for regular verbs, but also has its origina as the past indicative and past subjunctive of the verb "will" and so can sometimes include the meanings of "will" by itself. In addition, the word "would" can be used to describe regularly repeating events in the past.
