I would take a friend or mom or hubby with me for 3 that young.
if not it would be baby wearing, two year old in a stroller. Attach two car seats to stroller. Check third car seat and gate check stroller.
Getting all your stuff from the baggage carousel is going to be very difficult alone. Watching 3 kids, 3 car seats and getting a suitcase or two will be almost impossible.
Is someone dropping you off, picking you up? Because that is a lot of stuff to get to a car rental agency.
I have travelled with two preschoolers alone, that was more than enough. Getting them to the toilet on the plane is a nightmare.