We use a similar approach to getting new clients, but here are a couple of suggestions.
1 kill the chocolates they don't travel well in the summer, at least not in Dallas TX, and chocolate soup is not a good 1st impression.
2 coffee mugs are a good generic freebie, but would it make more sense to offer industry specific freebies. Perhaps a USB Drive or a mouse pad. Plus the usp/mouse pads are cheaper to mail since they are flat and light.
The connection between the free gift and the copy in the creative is a great idea (we use that). One more thing to thing about here one impression is not always enough. With direct mail 3 times is the rule of thumb, and we mail 5 pieces to each new client we are trying to win.
Whatever you do make sure you follow up your mailers with a phone call.