If your Power of Attorney is a family member, they may assist you with registering to vote and voting your ballot* but they may not do those things on your behalf without your presence (Wis. Stat. 6.875(6)(c)1). Your Power of Attorney may request your absentee ballot on your behalf.
*If you are in a care facility served by SVDs, they will need to be in attendance during one of those visits in order to assist you.