"If they had come, they would have been gone to Ngorongoro"
Translation:Wangalikuja wangalikwenda Ngorongoro
Kwenda can keep the kw the same places as monosyllabic verbs keep the ku, but it also can drop it. For example, “I went" can be nilienda or nilikwenda. This course pretty much consistently uses the "enda" forms although, both should be accepted once all the kinks are ironed out.
That being said though, I haven't got up to the -ngali- verb form yet so I don't know if that should can keep the kw or not, but even if it can, it's not obligatory, so wangalienda should be accepted too. Report it next time you see it.