Great Western Coffee Shop

Help please!
My lady is taking her Brownies to Calstock from Plymouth on 22 July, there will be 3 adults and 10 to 12 children.  She has to collect the fares from parents in advance, so needs to know the cost.
I've tried to understand Groupsave on the GWR website, but it is less than clear (to me anyway!).  Please would you experts give me the optimum arrangement.  There is a variable in numbers (10 or 12) as she is uncertain this far ahead how many will be going.
Also is this available from the TM on the train, or should she buy in advance (website or ticket office)?
Many thanks (on behalf of Mrs pb_devon).

Not an expert on the line ... but I would suggest groupsave for the adults (gives them 1/3 off).   These days, there is no children's savings on groupsave (special case of 2 adults + 1 child, where you buy 3 adult tickets a adult really means "any age"), so children's fares?   Except, perhaps, is there a carnet for children? - http://www.dcrp.org.uk/projects/carnet-ticket-schemes-with-local-shops/ .  Could also call the GW group booking line.

Plymouth have staffed ticket office, so you need to buy before joining the train - a pain as you'll get a big pile of tickets.  If you were starting at Calstock, the Avantix machine on the train could issue a much more practical ticket for multiple people (I have a ticket for 66 adults from one of the Santa trips we did!). You could also buy such a conveniently combined ticket a day or two in advance if you / she happened to be on the train at that point.

I'll echo grahame's suggestion of contacting GWR's group travel team. The GroupSave product is no longer a suitable option with a large children to adult ratio.

https://www.gwr.com/plan-journey/tickets-railcards-and-season-tickets/group-travel

When I worked for FGW, I once helped to organise a schools day trip from Combe to Worcester. Yes, I know, not possible, unless you arrange for special stop orders, which I did!

About 30 kids got on with a handful of adults. None of them had tickets. Much confusion about the cheapest way to travel. A call to the ticket office supervisor at Oxford elicited the suggestion of using Group 4, and charging some of the kids as though they were adults! No reason to stop you doing this, and, overall, it produced the cheapest price. So, once we had shown the TM how to do a groupsave on Avantix, the tickets were issued and everyone was happy.

Particularly when the driver remembered to stop at Combe on the way back!

Thank you grahame and BNM, also Oxman for the anecdote.  I hadn't understood that Groupsave wasn't applicable to childrens tickets.  My lady (or most probably me!) will contact group travel. 
I will endevour to let you know the outcome.

As a 'regular' organiser of group travel for Cubs and for my wife's Holiday Club, I would also recommend contacting the Group Travel team.

A non-update as 3 weeks on we have not had any reply.  Just submitted a hastener.

An alternative to consider if each of the adults had a Devon and Cornwall railcard. Breaking into 1 adult 4 child groups due to maximum 4 child policy on D&C railcard.

Offpeak day return with Cornwall and Devon railcard, total £7.85 (plus £10 railcard fee)

Groupsave offpeak day return total £17.35 (1 adult 4 kids)
For the 3 adult 12 child opetion
53.55 total with railcards including purchasing a Devon and Cornwall railcard for each adult.
Groupsave £52.05.
If any of the adults already held a D&C railcard it will definitely be the cheapest option to purchase a D&C for the other adults.

Also if further rail travel planned within the D&C area within 12 months as a group, the railcard option becomes the cheapest option.
Online can only book for a maximum group size of 9.

After the hastener mentioned earlier, we had a reply from customer services on 30 May saying they had looked for the first enquiry and hadn't found it, and asked for the details, which was submitted the following day.
Yesterday this email was received:

"Thank you for your email regarding tickets and fares. To find the latest deals and offers for your future group journey from Plymouth to Calstock  you can contact our Telesales team on 03457 000 125 they will advise you with the cheapest fastest routes or you can visit our website on www.gwr.com.
Thank you again for getting in touch and I hope this information was helpful.
Yours Sincerely
Darbi
Customer Support Advisor
First Greater Western Limited. Registered in England & Wales No. 05113733.
Registered office: Milford House, 1 Milford Street, Swindon, Wiltshire, SN1 1HL."

Words fail me!

Mrs pb_devon has now given up on the group sales thing (and chided me for suggesting it in the first place), and will pay a visit to the ticket office at Plymouth. It would be ironic if she was then told she should have contacted Group Sales!

Thank you to forum members for suggestions & comments.

Mrs pb has been arranging these trips every couple of years or so for long enough to recall a visit to the enquiry counters at Plymouth Station (remember them?  in a separate area from the ticket counter), and being told that a message would be sent to Laira to make sure there was a suitably sized MU set on the branch for that day.  Ahh those were the days!!

I'd call the number given. For groups or your size, they can offer prices unavailable at ticket offices.

Final report.
In the end we ran out of time, so a ticket office visit was necessary.
After checking a couple of options, the assistant came up with: Adults: Group Save £3.85 each.  Children: offpeak DR £2.90.

Mrs pb_devon happy with that.

Thanks to all above.