@D45ist ,
The travel agent that wants repeat business and does not want to have bad reviews would care about that "stuff."
The travel agent gets her or his business by providing a service. Travel agents do not necessarily quote you the low price to get your business, they get it by providing a service -- for example like the poster is requesting. The poster is requesting a special service traveling with a large number of people. My guess that is why the poster is using a travel agent.
Typically it is cheaper to book directly with the airlines - believe me I travel enough and have arrange travel enough for others not as savvy in finding travel deals.
And it is not true that you need to pay to book a seat. It is beginning to happen more often but it is not all that prevalent yet. It depends on the airlines and the situation.
As a matter of fact I just had family book a flight for my daughter - they offered to pay for her flight so they could see her over the summer - my only requirement was a direct flight and to sign her up as an unaccompanied minor (we would pay this fee). She is just old enough to travel on her own, but has never traveled completely by herself - prior she traveled with her older sister.
Any way they sent us a copy of the paper (as needed for this situation) and there was no seat assigned - I called the airline got her a seat -- no extra cost.
Similar to family that visited us recently. They did not have a seat assignment - as they were older adults, I called for them, spoke with their travel agent and he said we want to make you a satisfied customer and got a seat assignment - again no additional cost.
So you see --- two of my most recent dealings with the airlines and with a travel agent resulted in no charge for a seat assignment. So you would not necessarily know you would need to pay extra unless you read the fine print or in dealing with an agent that they provide the service they should and they make this clear.