Dear Rich staff lays in bed wondering if the apostrophe is still part of the MickyD mark -- y'know considering how domain names and Internet usage have decimated so many grammatical symbols. (Answer: Yes, though it was strange how hard it was finding the company name on their homepage.).
Right, you had a question. Assuming you own the copyright in the song, you can make a deal with McDonald's without creating a music publishing company. If you license the song, instead of assigning it, it wouldn't hurt to create a music publishing company; its primary function would be to collect money from performance rights societies in the event the ad is played on TV or on the radio, etc.
What about the contract? We think if McDonald's wants the song, they can work out any kind of deal, including one like the contract you suggested. However, we don't think that the contract is your biggest concern, right now. The major hurdle is convincing McDonald's to use the song. Most people in your position have a difficult time getting in the door to sell songs and for that reason, you may have a better time making a viral video hit and hoping McDonald's comes to you (and not with a cease and desist letter for diluting their mark). If McDonald's does express an interest, they'll either have a contract for you (time to hire a lawyer to review it) or they'll ask you to prepare one (time to hire a lawyer to write it).