As the main objective is make your kid happy, you better 就同學仔. Especially, if you are not so familiar with 同學仔 parents and/or they rely on helper sending the 同學仔 to the venue. However, I don't think going to New Town Plaza from Ma On shan is too far. I heard that there is a mini-van? Have you compared the facilities and spaces between the two McDonalds. Perhaps it is the more important factor to make the decision.