With YourSites you can install extensions on to your client sites.
You can install single extensions onto multiple sites at once.
Simply select the target sites on the site list page and click 'Install Extension', select the file and off you go.
Please bear in mind that post installation processing will not take place automatically. So if you install extensions that require a click of a link on the client site or the execution of javascript then YourSites will give you an orange warning and explain what you need to do on the client site directly to complete the installation.
We love every single one of our users, without you YourSites simply couldn't happen! So we would love a review at the Joomla! JED so we can let others know about us too, please take a minute to write a review:
https://extensions.joomla.org/extension/yoursites-manager/
If you feel you have something negative to say, we would implore you to speak to us first, as we really really don't want anyone to be unhappy!