For a little more diversification, I would amend that to buying shares of ITOT and IXUS in a 3:2 ratio (60% domestic/40% foreign), without paying commission if possible (e.g. https://www.fidelity.com/etfs/ishares).
Once you are comfortable with that, just rebalance this portfolio to the 60%/40% ratio once every year or two (http://seekingalpha.com/article/2130243-portfolio-rebalancin...), and start moving toward fixed-income funds as you get closer to retirement.