been at least 5 years since E&R boat. it ran at set times(hourly?). did not start til about 8-9am, and terminated at around 6pm. does not run off season(most of the time). charge was pp and put on your hotel bill. was about €30-35 then. the VCE concierge works very limited hours. in probably 20 or more trips thru vce, we saw him once. he does not do baggage. porters are seriously expensive in venice. some €6-8 per bag, and everything counts as a bag.

the trip from the baggage claim to the water taxi station is a paved walkway with NO steps. just use a rollaboard. i have always found a number of taxis waiting, and full assistance both into and out of the boat. i have never been charged for extra people or extra luggage.

if your MIL cannot make it to the boat, i would seriously reconsider venice. the place is stair steps everywhere.

there was(i do not know if it is still there) a booth in the terminal that sold a taxi ticket. std price, but paying at the dock works.

http://www.veniceairport.it/

map of terminal