RECOGNITION
The Recognition ceremony is also pretty common. You use it to swap holdings between domains as agreed per diplomacy. It can also be sued to seize uncontrolled provinces/holdings (for example those that just got Divested), but this is relatively rare.
The transfer of any number of provinces/holdings to ONE RECIPIENT from ONE DONOR constitutes one ceremony. So swapping stuff between two domains is really two separate ceremonies (I recognize your claim to my stuff, while you recognize my claim to your stuff).
Each ceremony costs 1GB and there is a +1 DDC mod per ceremony taken together (i.e. +2 for that classic swap). If you don't like the extra DDC mod, make it to separate ceremonies instead (but that of course takes 2 action and, if used, 2 separate Investiture spells). Your call.
BASE DDC
15 + province lvl for Provinces
5 + prov lvl + holding lvl for Holdings
Base DDC is 3 points higher than for Coronation/Designation. This is as it should be.
You've got more or less that same modifiers, but some stuff like synergy for example probably isn't going to happen, nor are your regent likely to support with an adventure. You might want to pimp the province prosperity a bit though; could be more cost-effective than NOT being able to take 10. And the Investiture spell is still highly useful if the initial DDC is too for you to make that Take 10 threshold.
But from time to time it WILL happen; the DDC is too high to Take 10 and you'll have to spend Influence to be certain of success. That too is intentional.