Its sounds like your extremely conservative, and thats ok. It won't make you rich, but if you sleep well at night, thats important. Actually you sound a lot like my father who it took me years (maybe decades) to slowly migrate money into investments.
Try to figure out a number of what in cash would make you feel ok. Is it one years worth of cash ($50K) or two years ($100k)? Plus your expected college expenses. Whatever it is, make it a hard number and then money above that can be moved to something producing more income.
Even if you took two years of income, you could split it 50/50 and put $50k in a 1 YR CD which would give you more than what you have right now.
Then look at dollar cost averaging some of that other money into the market. That way your not putting it all in at one time, you can split it up into as tiny of sections as you need to to feel comfortable, whether you take the exra $100K+ and split it into 12 months or 24 months or whatever, you can get it into the market slowly, but it should go into something. Maybe you even should go to a financial advisor (I know lots on here wont but if you are that concerned, finding someone else that you can trust may be a better option)... talk to friends/family, someone will know someone they do trust... again it doesn't have to be all of it, but maybe a small portion just to get you in.