I've not been in game since the switch to MQNext so I'm assuming nothing changed for that, but you could easily do this from your driver by setting up a social. I'm using EQBC terms, but just adapt for Dannet if you're using that.
/bct ClericName //alt activate 1212 (group perfected ivu)
/bct CasterName //alt activate 1210 (group perfected invis)
That should be it. That just tells the cleric to cast the group ivu, pauses for 1/5th of a second, then tells the caster to cast group invis. - All that's important for double invis to work is that the cleric starts the non-instant cast ivu and then, while it's casting, the caster casts their instant cast invis. So if the timing is messed up, you should only need to change the pause duration.
Keep in mind there is a different alt activate code if the ivu is being cast by pure casters instead, so adjust accordingly.