You are perfectly fine selling everything and using total market index funds. That is what most people recommend because it is easy and yet still has much better than "average" returns. For example, use 45% Total US, 30% Total International, and 25% Total Bond.
If you want to use a small fund as well that is perfectly OK but I suggest only one, because after that it can get complicated fast. I suggest Vanguard's small cap fund or small cap value fund as good choices because they are cheap and extend into mid cap stocks as well, so you aren't missing anything. The Bill Bernstein No-Brainer is a good way to do this:
25% S&P500, Large Cap Blend, or Total Stock Market
25% Total International
25% Total Bond (or a similar intermediate bond fund which includes treasury bonds)
25% Small Cap Blend or Small Cap Value