Can you approve what kids buy from an Android device?

Mami,

No. As in the document linked above, the options to approve an Ask To Buy request are "iPhone, iPad, iPod touch, Apple Watch, or Mac."

If you’re the family manager in the family group, you can choose purchase approval settings for any member of your family. If you're a parent in the family group, you can choose the purchase approval settings for family members whose accounts are managed with Family Link.

On an Android Device:

1. On your Android phone or tablet, open the Play Store app.

2. In the top left, tap "Menu" and then "Account" and then "Family" and then "Manage family members".

3. Tap a family member's name.

4. Tap Purchase approvals.

5. Select All content, Only paid content, Only in-app purchases, or No approval required