Has anyone used special assistance from St Pancras to Paris?

I am an elderly lady who has just been told due to a medical condition I cannot fly. I am therefore wanting to go via Eurostar to Paris. Has anyone used special assistance at St Pancras, and if so, what was your experience? Do they continue the assistance at Paris? I am not a wheelchair user but would need a hand with my bag and a shoulder to lean on getting down the platform to my waiting taxi driver at Paris.

Also, being elderly, and only knowing other ancient people, none if whom have children to show us, we are completely unused to and do not have smartphones, only laptops. Does St Pancras accept printed tickets and Qr codes and do Qr codes even show up on a laptop. My concern is getting to St Pancras, which is 100s of miles from my house, and then being turned away if I can't get through the gate.

Any help with these issues would be greatly appreciated. Thanks to you in advance.