Translation:The mother and the child usually go to the clinic
Any correct translation of the source sentence into the target language should be accepted, especially since the sentence may come up in general strengthening exercises, where it's not clear which lesson a sentence comes from. So English "[The] mother and child go to the clinic" should accept Mama na mtoto wanaenda kliniki and Mama na mtoto huenda kliniki. If they're not accepted, it should be reported.
For verbs that have a "thematic vowel" (final -a), that vowel needs to change to -i for negative present, so "you (sg) don't go" would be huendi. However, for a verb like kusafiri that doesn't end in -a, I believe the negative 2sg present form and the habitual form would be homonyms.