I'm not sure on all the differences between LVN/RN, but I can tell you I decided to go for my BSN over the LVN for several reasons: one, for the increased amount of autonomy the RN has vs. the LVN; two, and it may sound crass, but the money is quite a bit better (I'm 36 and don't have as many years to "climb the ladder" as you would!);three, the advancement possibilites are far better for an RN than LVN, though I have met some LVN's that were charge nurses (in the SNF unit).
If you have the time, you have to weigh your options on which to select: it will take longer to obtain your RN (about a year or so for the program and prerequisites), but then you have it. To obtain an LVN, then upgrade to RN seems to be a bit harder, as you probably would be working while trying to get your degree (an LVN is not a degree, but a vocational training program). Personally, I feel going straight for the RN is a better option, whether you go for an ADN or BSN.
While doing clinicals, I was working with an LVN that had 12 years experience, and knew nursing inside and out, but I, being a lowly nursing student, was able to administer and IV medication where she was not able to do so. I found this quite interesting! Of course, she knew how to do it, and why, but her license would not allow her to do this, and had to rely either on an RN, or me, an RN student, to deliver the med. I felt this seemed a bit degrading for her, but she never showed it.
I would recommend that you go into a hospital and ask the RN's and LVN's their opinions on why they chose what they did (of course, if you can catch them! They're awfully busy!)
I'm not sure if I answered any questions for you, and hope some seasoned nurses out there will reply for you. I just thought I'd give you my opinion, since you are just slightly older than my oldest son (god, that makes me feel old!), and would hope someone out there would give him some advice when he asks for it. Take care, and welcome to the wide world of nursing!