You can try, but absolutely make sure they don't try to cancel and rebook for you though! It is possible to modify (a dining CM has been here before and confirmed it), but not all CMs may know that they can, or even how to do it.
In the end, it's not really going to matter either way. They don't hold tables for normal ADRs (unsure about the large party ADRs they get from time-to-time, but up to 10 or 12 I'm sure they don't), they simply assign the table for the party size you show up with when you check in.
(Note: Boma does not require a CC-guarantee at this time.)