Question on TS credits
 

If we are on DDP and have someone eating with us who is not, can we use one of our TS credits to purchase their meal?

No, I have had servers not ask who is with whom and take the TS credits off one card. But everyone was on the DDP and we were family so we worked it out. But no you may not share.

No, the dining plan states that you cannot use your TS credits for someone not on your room reservation. Also your KTTW cards will state xAdults and xChildren so your server will not be able to take more credits what is on your card.

We only ever go as a family and so everyone is on the plan BUT we have had times where we have seperate rooms & so the meals are on different cards, yet in loads of places the server took the meals of 1 card even though the card said 2 adults 2 kids not 3 adults 3 kids???

The servers usually do not take 3 adult meals off a KTTW card that says 2 adults, but perhaps it had something to do with your having one resort res with 2 rooms :confused3 I would just be worried that near the end of my trip I might have a stickler of a CM who won't deduct all the credits from one room after all the credits had been used up on the other room. I'm sure it would be straightened out, but it would take time out of my day to have to deal with it.

In any case, the OP only has one room and the DP rules do state that you can't use credits to treat someone.

Thanks for the info. I kinda figured they wouldn't let us do that.

Nope, not supposed to. Per the WDW DDP FAQ site:

Q. Can I use my Disney Dining Plan to redeem meals for friends or family members who
are not included in my reservation or have not purchased a Disney dining plan?
A. Sorry, you may not use your Disney Dining Plan to redeem meals for friends or family
members who are not included in your reservation or have not purchased a Disney
dining plan.