I was in a similar situation as you, but my son is only 4 1/2. Almost 2 years ago, I met a man 10 years my junior (I'm now 37, he's 27), and he is the most mature, dependable, loving man I've known. We are now engaged and looking forward to expanding our family. No training required. If you had asked me before I met him if I'd ever consider dating a 20-something, I would have laughed, rather hysterically, in your face at the ridiculousness of the suggestion, as we all KNOW that guys in their twenties are mere babies, and in no way ready for any of the responsibilities of the real world, or better yet, a family.
All I can say is, I stand corrected. :)
Keep your daughter's needs in the forefront of your mind. Trust your instincts. And live your life the best way you can for your family.
Best wishes!! I'll be hoping for you that your 20-something is as good as mine!