I have not done the rental car bus for a long time but some of my concerns:
1 - don't LAX Rental Car shuttles drop off at the upper level and pick up at the lower level?
2 - the driver might ask you for your name to confirm the reservation when you get on
3 - if there is no one at T7, it won't stop and you really can't have a logical story to explain why you did it and want to get off at T7
4 - it will slow down other passengers on the bus - OP has 4 big bags and a child