When someone is in the throes of death, those present should gently prompt him (talqīn) to say "Lā ilāha illā Allāh," without harshly ordering or pressuring him, for the Prophet ﷺ said: "Prompt your dying ones to say Lā ilāha illā Allāh." Whoever's last words are this testimony has been promised Paradise. It is also good to speak well in his presence — since the angels say "āmīn" to what is said — and to make duʿāʾ for him. Once he has uttered the shahādah, one does not keep pestering him to repeat it, lest in his agony he say something inappropriate.
Informational, not a personal fatwa. Consult a qualified scholar for rulings on your situation.