Ok, then yes, you can use them for SDFP. You will just have to keep in mind which MBs are for park entry and pre-scheduled FP+, and which are for SDFP.
In fact, in that scenario, you should be able to prebook FP+ using that
MDE, 30 days in advance. Just make sure you keep the MBs straight.
Here's the thread that explains maximizing FP+ using multiple MDE accounts:
MAXIMIZE FP+
Have a great trip!