I believe (but am not a contributor to the course) this is because Gaelic does distinguish present habitual and continuous, and in Scottish English people do say things like I am seeing… in the present moment meaning.
The better translation of I see children to Gaelic would be Chì mi clann (which has both the present meaning I see… and future I will see). But the Duolingo course doesn’t teach the future (which also works as present habitual) tense yet (I think it might come later in a new version).
Anyway, the course basically requires you to translate all a’ + verbal noun and ag + verbal noun constructions to English continuous tenses (the be + verb-ing ones), except for future sentences which can be translated either as future continuous or simple present (eg. bidh mi ag òl – I will be drinking or I drink) since the future tense of the bi verb also has the present habitual meaning of be.
Spot on. Where English uses simple present for an immediate event, Gàidhlig uses the progressive present formation above, in most cases. Likewise, the simple present formation (which isn't really present per se) covers instances in English that are both present and future tense.
Gàidhlig looks at time a little differently than English, as is common with differing languages and cultures, so English doesn't map neatly 1:1 onto it.