That sounds great. When you check out the DNA tests, you may want to look at the mtDNA test which is used to get information on the direct maternal line, where the y-DNA test provides information on the male line. Since Emma is the possible link to David Rittenhouse Porter, it may be the maternal test which will give you the best information on her line. You may want to talk to the people at FamilyTreeDNA and ask them some questions to make sure. I do know they have a sale going on right now for the mtDNA test. It is only $139 instead of $199. You can order it online and have it sent to your father as far as I know.
I look forward to hearing from you once the test is complete, whichever way you decide to go.