1st I would call the Garden Grill directly and ask. the CM's at the ressie phone lines might not know and just say no.
I also think you could make the Ice Cream they give you a Birthday Treat in place of a cake. You get a frozen plate with Choc. swirls. A tollhouse cookie that has been dipped in choc. holding up a 8 inch high sugar cone that has been dipped in choc. Breyers Vanilla topped with sprinkles, gummy worms, whipped topping, a round wafer cookie, etc. etc.
It was really good.
our little boy (16mo) just had a bowl of ice cream and they did not charge for him. Then "Chip" came by and spoon fed him for about 15 min. it was great.