Brian hit a lot of good points on the difference between "video conferencing" and "web conferencing" (web conferencing is also often referred to as Unified Communications). So, the first thing that needs to be answered is, do they really need full-blown video conferencing, or just web conferencing?
Some other things to think about or ask:
1.) They say they want to do a demo for about 10 people. Are those 10 people in a single location, or are they 10 individuals that would be connecting from different locations? Stated another way, do they need point-to-point or point-to-multipoint conferencing?
2.) Do they have control over what type of system (hardware and/or software) the remote end points are using? As an example, my company has offices in Dallas, San Diego and UK. We often have presentations or company meetings at our Dallas office that the San Diego and UK people will attend via video conference. In that case, we have control over the hardware/software for all of the conference end points. Conversely, if they need anyone to be able to connect from anywhere and they don't know what systems they have, they may need a "conference bridge" service (aka gateway) such as BlueJeans. This would especially be the case if they need "real" video conferencing and need to connect end point codecs from different manufacturers. Cisco, Polycom, Lifesize, etc. typically don't talk directly to each other. Cisco and Polycom have their own conferencing bridges that can be purchased but they are ridiculously expensive, especially when you get into higher numbers of end points. Unless they do these video conferences all the time, it more cost effective to use a conference bridging service and just pay as they go. Also note, pretty much all of the video conferencing hardware manufacturers also provide apps for desktops/laptops or mobile devices. That means (for example) a Polycom hardware codec in their main demo room could conference with a bunch of laptops and mobile devices running the Polycom app as endpoints. Additionally, most of these hardware codecs can also connect with Skype for Business/Microsoft Lync without requiring a gateway.
3.) Do they want/need archival recording of the demos? Perhaps they want to be able to put links to videos of past demos on their web site? If so, that is a whole new can of worms and there are a large number of can openers you can use to open it.