It absolutely all depends upon the age of the child when adopted. I adopted two toddlers (under 2 years old) and maintained membership in ethnic organizations, celebrated their holidays with ours, etc. Ask your case worker, she's the best source of advice. With that said, however, follow your instincts too! Our pediatrician told us child must sleep in own room from day one. We didn't realize they'd slept communally since they were born. I still could tear myself up about that, I feel so bad, I let them cry and cry just because dr. said to. What an ass I was. Follow your heart.
