In-App Purchases : Different ID's?

So I have an iPhone 5 and I can't make any kind of purchases with the apple ID that I'm using. But I want to sign out of my apple ID on my iPhone and sign in with a family member's ID which can be used for purchasing and stuff... the problem is, when I signed in with the 2nd ID, it wouldn't connect to the iTunes Store when I tried to make an in-app purchase.. I read some forum posts that said it's not possible to make in-app purchases with a different ID than the one that was used to download the free app in the first place.. So my question is.. If I deleted the free game while I'm signed into my ID, and then sign in with the 2nd ID, and download the game again, will it let me make an in-app purchases? because, theoretically, that way I should be able to buy the free game AND make in-app purchases since I'm doing both while signed into the same ID.... Will it work? I'm just asking because I don't want to lose all the progress on that game for nothing if it doesn't work...