Can I ask a buyer to sign an NDA on behalf of their whole team, not just themselves personally?

Yes, and this is standard, sensible drafting rather than an unusual request. Rather than requiring every individual on a buyer's team to separately sign, most well-drafted NDAs define a broad "representatives" clause — covering the buyer's employees, officers, advisors, and financing sources involved in evaluating the deal — and make the buyer contractually responsible for ensuring those people comply, and liable if one of them doesn't.

This is generally more practical than chasing individual signatures from everyone who might touch the information, and it's the approach most experienced buyers will expect and accept without pushback. If specific individuals will have unusually sensitive access — someone reviewing highly confidential material directly, for instance — you can still ask for a separate acknowledgment from that person as extra assurance, on top of the broader representatives clause rather than instead of it. What matters is that the definition is broad enough to actually capture everyone who might see your information, and that the buyer remains on the hook for their team's conduct. A Treadstone business lawyer can make sure this clause is drafted broadly enough for your situation.