I never had a problem texting on flip-phones. My first four phones only had the number pad keys, I texted just fine.
If you want to make multiple texts per day, and essentially write email-length texts, yes it is a pain. But I could text efficiently using both T9 and the standard letter system (tap each number multiple times for some characters).
And my mom has learned how to text in the last year or two, and does so using a standard flip phone.
As was stated by another poster, if our moms can figure our texting with flip-phones, I don't see the huge issue. And like I said, I thoroughly remember texting on flip-phones.
But with that said, I don't know if there are any great flip-style phones with keyboards anymore. I know their used to be a few out there, the Samsung Alias, that was a flip-phone but could also flip horizontal and the keys turned into a QWERTY pad (e-ink keys).
My buddy had that phone and loved it.
I couldn't find it on Verizon's site, but phonearena has not updated by saying the phone is discontinued.
Samsung Alias 2.
that's about your last hope if you still demand a feature-phone without a touchscreen. There are quite a few featurephones with QWERTY, but they have touchscreens, and tend to be sliders or horizontal clamshells (those might be dead now too, hmm...).