May i suggest calculating your dad's cash flow for the next few months, then using that as a basis for decision?
eg. If his cash flow is good / recovered within 1 or 2 months, heck, why not do credit card for the flexibility.
However if his cash flow isnt good for at least 6 months+, then U may want to consider re-mortgaging the car

Serong a bit:
Any thoughts of taking a top-up mortgage loan or remortgage a property? I mean, IF the amount that is worried about is big enough to warrant it, mortgages are the lowest interest charged BUT one does have to pay the legal fees and the lock-in periods.

In addition, what about "soft loans" from relatives, say at a good 6%pa or 8%pa at daily rest? Win-win situation as relatives with FD lying around making 3%+pa will get double or more + your dad saves $ on interest AND the $ is kept within the family circle.

Just a thought 
Merry Christmas to all, and to all a blessed new year.

Top-up mortgage loan is only applicable if he has an existing mortgage.
ie.
Say loan was K for a K property (90%).
Paid down loan to K already now + property now worth K
He can try to get bank to give him a top up loan of K or less  ( (K *90%) - K )

Your dad's right in the sense that it may not be worth "risking" a property + legal fees for like K loan.
However, if he uses some sort of flexi mortgage, like those from Standard Chartered, Alliance & UOB, he may churn/cycle the $ for business cash flow when needed.
Flexi mortgages - U can knock down the principal amount any time/any amount AND re-draw the extra payments any time / any amount via cheques/ATM/online.
When U pay extra / knock down the principal amount, say K, U dont pay interest on that K UNTIL U re-draw it
eg (simple example only, not spot-on actual mathematically same with banks).
On top of the monthly payment, i plonk in K additional on Jan 1
Then later, I took out K to buy stocks on Jan 31
a. My mortgage interest calculated from Jan 2 to Jan 30th would be less K *x.xx%/364.25 days (mortgage interest charged) *28 days
b. From Jan31 onwards, my mortgage interest calculated would be K *x.xx%/364.25 days (mortgage interest charged) *xx days

Credit cards debt  (i'm all to aware of them - had profound experience with it earlier) - unsure how it works nowadays but the concept is similar
This was how it hit me in my younger & dumber days:
1. Say end Jan statement U owe K, paid K
2. Now, the K owed attracts interest + U get hit with some fees or other (? ? ?)
3. In addition, any additional amount U swipe on the credit card in Feb will automatically attract interest straight away
Due to the above, my effective rate of interest was about 20%+pa! Those days lar - nowadays unsure whether as bad, better OR worse.

Since we're serong-ing a bit, how about tapping EPF A/C2 if your dad has a mortgage?
Do monthly withdrawals - there is a purposefully loophole in which i think the Gov left in there for people to use that amount for OTHER reasons than strictly paying off the mortgage. The yearly withdrawals is a different animal altogether.

Note - please check with your friendly bank & epf officers for exact T&C, i'm just a working ant with (some painful) experience