Why would thirty companies each get a vote? Because that is what the charter says. There wouldn't be one parent company, rather the real estate would be owned by them all directly as tenants in common.
> 9. A. (2) Non-residents. Every property owner as of March 1 prior to the annual municipal election, whether a natural person or artificial entity, including but not limited to corporations, partnerships, trusts, and limited liability companies, and who is registered to vote, if provided by ordinance, shall have one (1) vote. A natural person shall be a citizen of the United States and age 18 on or before the date of the election. An artificial entity shall be a domestic entity in the State of Delaware.
https://charters.delaware.gov/fenwickisland.html
So they must be Delaware entities. Another thing I'm giving up on is that the Series LLC might not work. While each Series is legally independent from the others, I think they still might not be considered distinct "entities" (once again, not looking to give myself a headache to solidly determine that).
So either do one LLC/corporation per vote, or perhaps trusts might be even cheaper (no idea what filing/recording would be required for trusts, especially to substantiate them enough to register to vote)