We've had some good discussions here about target retirement fund vs build your own. I believe building your own is easy and saves you money, so I'll throw in my 2 cents.
I have a TD Ameritrade account myself, and as you probably realize, all of those funds you mentioned trade commission free. That's a pretty big deal, whether you're investing a little at a time or a lot. Which in your case it's definitely a big deal. If you purchase a Vanguard target retirement fund on TD Ameritrade it's going to cost you a $10 commission.
The expense ratio on a Vanguard Target Retirement fund is .18%. The expense ratio on every fund you mentioned ranges from .05% (VTI) to .19% (VT). Assuming you skip VT, you are going to save money on fund fees by going with individual funds instead of the target retirement fund. Even if you include VT, your overall portfolio expense ratio will be lower.
The benefits of a Target Retirement Fund are in their simplicity, but since you seem to have a good handle on how to build a properly diversified portfolio, you're already beyond the need to invest in such a fund. Save yourself the commission and the higher expense ratio and go with those commission free ETFs.