For help for children dealing with euthanasia and pet loss, go to these pages at the Human Animal Bond Trust:
Children and Euthanasia
Helping Children Deal with the Loss of a Pet
Midwest Cremation Service of Wisconsin has many options for memorials, like a variety of urns, memorial plaques, and jewelry charms.
The Rainbow Bridge is a grief support community. They have resources for grieving, memorial options, and more.