Towncars will fit a seat and a booster but will be tight in the backseat. Depends on the size of the seats. If your child is 4 and above he can be accommodated in a regular seat belt if you desire, by Florida law, under 4 you need a baby seat. If you just plan to visit Disney and stay on the property you may not have to carry your seats with you. Most companies can provide the needed seats to accommodate you, free of charge. One good idea is the hiring of an SUV, which is the equivalent of town car vans. An SUV will be able to accommodate your needs, plus groceries if you would like to pick up groceries on the way to Disney.