Although I use my Marriott points differently (I do stay at Marriott hotels, and I sometimes do use the travel packages), I tend to feel that it is a good use of your points if it meets your travel goals and you are satisfied with that redemption.

About cancellation: Chase is very good about allowing you to transfer your credit line to another Chase credit card. So if you decide to cancel your Marriott credit card, but have another open Chase credit card, I would ask the rep to transfer your Marriott credit line over to your other card(s). That way you will retain all of your Chase credit line. In the future, if needed, you could then transfer some of that retained credit line to a new credit card account that you might wish to open.