Two minutes. You will get one private page for yourself, one link to drop in the group chat, and one private link per person to send them.
However you already say it in the chat.
Rough is fine. "Not decided" is also fine — say so.
If you only have "spring break", write that. Pinning it down is usually the first real job.
What everyone will be quoted in — flights out, the house, the lot.
One row per household, because money is a household question and dates are a personal one. A couple is one row with two names. Everyone gets their own private link either way.