I wouldn’t recommend it as it would shift their intention to getting the prize rather than to obey Allah. If this was a once prize, this may be ok but to give it over such long duration, I wouldn’t recommend it.

A brother in charge wants to offer prizes (gift cards) for the kids who attend fajr prayer 3 times a week, for the first week 25$ value, if they continue for the second week then they would receive 50 and if they continue for the next couple of weeks then they would get a $100 gift card. What do you think of this as an encouragement for them?