If a table wants to split their check, we recommend the payment be fully captured on sunday or fully on the POS (traditional way).
If you do want to use 2 different tenders still, the sunday payment should be processed first then the team should tender the remaining balance to Card / Cash on Toast.
You should not combine split types (i.e. split the check 3 ways on the POS, then have the guests pay with sunday, as it limits their optionality).