I would say go for it but make sure it is understood and that a contract between the 3 of you is signed and have it stating that at any time there comes a problem that they start getting jealous of each other spending to much time with you and not with the other. Tell them both that the one who starts complaining the most will be the one being removed from the group. I have a ? for you tho. Are they both Submissive or are do they just like to play games on you?
You could go storiesonline.net and look for the Author mypenname3000. Click on his stories and look at the top Left area that say Series Universes. Click on Universes and go down the list to The Incestuos Harem and read that story to see if you and your 2 girls are anything like it is discribed in that story.
Best of luck to the 3 of you and have fun. I shall be looking forward to seeing how the 3 of you are doing. Ralph
P.S. Tell if it works for you 3 . If it does then I will know how that The Family Roles have changed.
P.S.S. I will be looking forward to hearing from you and I have some news as well. The Senate and House are still fighting as they climb