To my knowledge, we don’t use a certain style of writing. I taught manuscript letters while teaching 100 Easy Lessons, since the lessons require the child to write the sound they’re learning. We used that style of letter until this year when we’ve begun cursive. I don’t know what style of cursive I’m using either. The book I’m following is A Reason For Handwriting: Transition.
In your situation, I’d teach whatever you feel they’re ready for now and stick with that style until you’re ready to begin cursive. No reason to teach two styles of manuscript, in my opinion. If you’re going with D’Nealian cursive, perhaps it would be easier for them to learn D’Nealian manuscript.
Hope that helps,
Lindsey