We just lost one of our labs in December due to the same thing. Sarcoma tumor in her mouth......we did antiinflammatories and steroids and some pretty hefty pain meds for about a month, at which point we were maxed out and she was not doing well anymore. We told our kids who were 3 and 4.5 years old at the time she was diagnosed that she had a big boo-boo in her mouth called cancer that could not be fixed. We said it might not be much longer that she can stay with us, but we will keep her here with us as long as we can do it and keep her comfortable. I explained to them when the time comes that we can no longer help her stay comfortable and happy, it will be time to have the vet. help her go to Heaven. I explained that the vet. had special medicine that could help Taylor go to Heaven without hurting her at all, and that she would no longer be in pain. I explained when the time came that she was in pain even though we had done everything possible for her, and it was time to say goodbye and let God take care of her now.....that only God could fix the cancer in her mouth and make it so she could eat, drink, bark, and be happy again. They didn't like seeing her in pain when the day came, so they understood that she would never feel pain again when she went, and that gave them great peace. I had our vet. come to our home, so they were able to kiss and hug her and say goodbye, but then I put them in their rooms for nap time for the actual euthanasia so that they didn't have to watch. My older child had asked if he could see her one more time afterwards, so we let him come and kiss and hug her one more time after the vet was done for closure....but our youngest chose not to come see her once she had passed, and that was fine with me. Dog Heaven and For Every Dog an Angel were must-reads in our house, and they still read them very often....digging those books out on their own. They both have a black lab stuffed animal that they sleep with and carry around, and talk about her every day and pray for her every night. It's been 6 months and it is still on their minds daily, even though they are young it really does affect them, so it's good that you are being sensitive to their emotions with it all. Hang in there, I totally feel for you on this one, it is not easy when our furry friends get sick :( They really liked getting to help with the medicine while we still had her, I told them she would always remember and be thankful for how great they were with her....I would wrap he pills in a pill pocket and they took turns giving it to her...they loved helping her in any way they could.....hand feeding her with soft food when she couldn't get it out of the bowl, and handing her medicine really made them feel included and like big helpers to her.