Definitely send a thank-you note, but (IMHO) generic "thank you for the nice gift" notes are only a little better than no thank-you at all.
For the fruit basket, he could say something like "After being surrounded by holiday junk food for weeks, the fresh fruit basket was a wonderful treat."
For the money, mention something nice he was able to do using the amount given. For example, for the $50 gift he could say, "I used your gift to treat my wife to a nice dinner out." (Of course, then he has to actually DO it!
I buy my hairdresser a nice bottle of champagne every year as a thank-you for her services. She never fails to send me a prompt thank you note back, and I never fail to be charmed by it.