No, you can't use multiattack on a charge.

The Charger feat, from page 165 of the PHB:

> When you use your action to Dash, you can use a **bonus action** to make **one melee weapon attack** or to shove a creature.  
If you move at least  10 feet in a straight line immediately before taking this bonus action, you either gain a +5 bonus to the attack’s damage roll (if you chose to make a melee attack and hit) or push the target up to  10 feet away from you (if you chose to shove and you succeed).

Multiattack is an action that allows you to make multiple attacks. This does not mean you can substitute it into anything that gives you an attack. The Charger feat lets you make one melee weapon attack as a bonus action, and that's all you can do with it.

To be able to use multiattack, the Charger feat would have to say something like: "When you use your action to Dash, you gain another action."