Have them design it and then use a local printer to print and mail. Most printers should be able to take the mailing list you have from QB and mail out on your behalf. Or if you want to save money have the cards printed from an online printer (we have been very happy with quality of things from Overnight Prints. We just upload the files our designer made and have the stuff in a few days). You can convert your QB mailing list to Avery label template and print them out yourself. Then when you get the post cards from overnight prints, put the kids, wife, significant other to work attaching labels and stamps while they sit in front of the TV and then drop them off at the post office.
I have finally begun to input all my customers from my first few years of business into an Excell spreadsheet so I can start mailing out reminders and specials.
I have considered using a marketing service to do the mailings, but have been disappointed with the limited template selection of all the ones I have looked at.
Of course custom cards can be created, but in regards to templates alone, if one has the time to do the actual label printing and mailing themselves, they can choose from hundreds of different templates from hundreds of different companies/printers, as opposed to being limited to only the templates available from the particular company you are using.
I have used the Avery label software before and it's a breeze to merge your contact list and print them using their 30 label per sheet pages.
For someone in my shoes, who doesn't mind taking on such a project themselves, and whose 3 young kids work cheap, I see no reason to limit myself to the few templates of one company, when there are so many different ones available collectively from all the different companies, and if custom ones are created, it's possible to source the best price from independent printers.
