No, you can't. When, if, unless and as soon as are all followed by a present tense (present simple, continuous, or perfect) in future sentences. Your sentence should read:
'If the children are sleeping/ are asleep when you come..'
2 mars 2015
1
2
Vous n'avez pas encore trouvé vos réponses ?
Écrivez vos questions et profitez de l'aide des locuteurs natifs !