How do you link the records in your filemaker file? Hopefully, you have a serial number field that functions as your primary key.
Is this a one time import of unique data (one line for each donor) or something that you will do over and over again with the same doners possibly being imported multiple times?
Donors with the same name who may or may not be the same person represent you biggest challenge here.
If this is a one time import and the same donor isn't listed more than once, you could import the data twice--once to each table and then use replace field contents to assign matching serial numbers to the newly imported records. (This works only because there is just one line per donor and the record order in both tables immediately after import will match the order in your csv file.
If this is something you need to do repeatedly and/or a donor may be listed more than once, you'll have to design a system that matches by names in order to assign matching ID numbers and this can get messy if two of your donors happen to have the same name.
Import twice, once on the layout based on the first table, once on the layout based on the second table.