It is ok if that is to extract the Bitcoin on that key's address, but yeah, never re-use the address and dump that key after retrieving what is on it.

The effectiveness of gifting Bitcoin is dependent on the person receiving the gift.  If he is a newcomer and has deep interest on Bitcoin and how it works, I think the gift effects would be at its maximum since the person will be interested enough to dig into the information about Bitcoin, how it works, how to transfer and how it can be spent.  This way the newbie who is new in the field will have a practical or hands-on on the things that need to be learned about Bitcoin.