You are able to do what you're wanting
Either take your time with it on their website or stop by RadioShack or Best Buy to ask them there.. I'd stay away from a Corporate Owned Sprint store or from their customer service on the phone
Just tell them exactly what you want
3 lines just TALK
1 line with Everything Data (make sure you let them know which Everything plan you want because there are a few, Simply Everything is 99.99 a month where as Everything Data is 69.99 a month this doesn't include unlimited anytime talk... it does include Any Mobile Any Time though, which means the minutes you use calling ANY cell phone doesn't count against your anytime minutes... what does count against your anytime minutes are calls to land lines)
My girlfriend has two lines on her account, one is Simply Everything and the other is the Basic plan, which is only talk for her grandmother