daisy a verbal thank you would indeed be enough. You don't get many of those. I have to say too that, as a Rainbow leader, I can't think of a single volunteer who does it to boost their CV or to gain experience. We have a few younger people who come and help us as a part of their Duke of Edinburgh and I suppose that's of wider use to them, but I'm not going to discourage them!
If anything, several people I know (myself included) would actually like to give up volunteering so that we could have more time with our families etc., but if we carry on because if we stop, the units will close. It is lovely when we see the kids enjoying an activity, of course, but that doesn't help when you're battling the online membership database or cursing the Girlguiding policy that online banking is banned, so you have battle through town on a Saturday morning to pay in a cheque for £1.50.
On another point, obviously teachers spend more time with the children than Guiders or sports coaches, but sometimes we are confided in because we aren't at school and part of the system ("Child A is bullying me, but I don't want to tell Mrs Teacher because she likes her").
To be clear, I really do not expect presents, and it doesn't worry me at all if people would rather buy for the teachers or TA's or whoever. It's lovely when people do think of us though!