my daughters came home with exemplary amazing report cards that they worked very hard the whole year and especially during this last very hard period of time learning over the phone etc... I was wondering if I could take them out for an ice cream as a token of appreciation or wait till after 9 Av?

ב"ה Shalom First, allow me to wish you much more nachat from your children. There is no real prohibition of going out for an ice cream or a cup of coffee during the nine days. Halacha outlines for us what is prohibited. Although, we don't seek to go out for additional pleasures, from your description, taking your daughters out for an ice cream is completely an educational act of rewarding good behavior and you do not have to delay it. However, if you think you will feel more comfortable taking them out for ice cream after the 9 days, just as a suggestion, you could possibly tell your daughters that they will get an extra scoop if they have the patience to wait. All the best