Should I apply for an EB-5 EAD or EB-1C if I have the option?

It is okay to apply for as many immigration benefits as for which you qualify. It is my opinion that you do not have to disclose your EB-5 dependent status to your employer unless you want to do this. What would you hope to gain?

The EB-1C process will be quicker and provide you and your family with a permanent, 10-year green card, as opposed to the conditional 2-year green card from the I-526 petition. You can have the EB-1C process moving in parallel with your EB-5 process. Moving forward with the EB-1C first makes sense to give you the opportunity to obtain a permanent green card - if this process fails, you will be able to adjust status based on the EB-5 petition.

EB-1 route definitely as that gives you the 10-year card and the EB-5 route just the 2-year card.

You can clearly do both, although sometimes USCIS wants you to choose. The L-2 is also work authorized. You probably want to disclose your EB-5 dependent status so the lawyer filing does not inadvertently omit information.

You should file every application you are eligible to file. There is no law that requires you to notify your employer you have filed for adjustment on a different basis.