Villagers in boats will not become willing to breed.
They won't accept food (see https://bugs.mojang.com/browse/MCPE-31526 ) but you can trade with them. Trading with them while in the boat does not trigger the willing to breed hearts, however.
Filed as a separate ticket since it also applies to trading.
If there are two villagers in the same boat, their hitboxes should be touching, so after becoming willing to breed they should have a baby villager soon, as it works in java.