A suggestion for the ship's spells:
- The Floating House: Re(Mu)He(Te) based on The Hut remade. It will allows to travel to any location and settle for a while, without drawing too much attention.
Depending on how big is the ship, you could invent a spell to turn into a cart or several ones to allow for transport accross land and sea - without resorting to the usual flying ship.
If the ship is carrying horses to be used to pull the caravan once the ship is turned into carts, then probably a spell to control and sooth the horses would be useful - it will manage to keep horses under control despite the presence of Gifted individuals nearby.
Since there is little Herbam specialist in your group, maybe you build a stone ship, and make it float and stir through spells, and hide its unusual appearance through Imaginem.