I'd talk to your mortgage lender before trying to put your down payment on credit cards. Going into debt for a down payment on more debt doesn't make a lot of sense. Before closing on your house the mortgage lender will pull your credit reports and possibly want bank statements, and will probably ask where you are getting your down payment from. Racking up massive CC debt right before closing will raise a HUGE red flag because it will skew your debt to income ratio.
Even if you could somehow convince the lender to go for it, the problems don't end there. Seems like you would basically be getting a cash advance, which has a way lower limit than your overall credit limit usually, and is subject to interest immediately with no grace period, and at the cash advance interest rate which can be pretty high. You might end up overextending yourself so crunch some numbers and make real sure you can afford to do this.
You might be better off looking into mortgage programs that require little to no down payment - are you eligible for a VA loan? If not, look into an FHA program. Here's a helpful link from Bankrate:4 mortgages that require little money down
Good luck on the house, hopefully you can figure something out that makes sense and is affordable in the long run.