You can include both of them in the same update site, here is some additional documentation on update sites
Title: Methods of pushing down Sametime 7.5.x & 8.0 client updates
Doc #: 1256320
URL:
http://www.ibm.com/support/docview.wss?rs=899&uid=swg21256320
unfortunately after the update site is applied the client will have to restart.