Yes, tough spot, but the ripples from this will die out and not affect your R with your W as long as it is handled without rancor and your are fair and justified in taking the measures that you do.
But, whatever you do, watch about undercutting W's mothering. One way to approach this may be to combine praise with boundary setting : "It is great that you want to push S5 to learn from these camps, but (something to the effect that it is blowing your bank acct.)".
Now, I have to agree with Wes about the giving up the coffee thing. I am dissapointed in you. Think of all those poor coffee farmers in Guatemala and Colombia and Kenya. How can you deprive them of a livelihood? And think of poor old CEO of Starbucks. What about the upgrades to his yacht?
UD
The 3 laws of DBing:
1. PMA is critical to DBing.
2. Since drop in WAW's PMA leads to drop in LBS's PMA and vice-versa detachment is critical.
3. Validate to raise WAW's PMA and GAL to raise LBS's.
Think of all those poor coffee farmers in Guatemala and Colombia and Kenya. How can you deprive them of a livelihood? And think of poor old CEO of Starbucks. What about the upgrades to his yacht? 
