Bob = you will have to check the AC INPUT specs on the new charger. Your HONDA EU1000i probably only gives you somewhere around 850-900WATTS of juice.
If your 50AMP Battery charger draws more than the 850-900WATTS then the Honda EU1000i will not be big enough to power up the unit. Especially if you are connecting the trailer 30A Shore power Cable directly to the Honda EU1000 120V receptacle. You may have connect the new 50AMP Charger directly to the Honda EU1000i to do this.
Check the 120VAC INPUT Specifications of the new 50AMP charger to see if it can be done or not... Also you will want to purchase a SMART MODE charger if you are expecting to be able to re-charge your batteries in a short three hour generator run time.
Be sure to check all of that out before you purchase something that won't run being plugged into your Honda EU1000i unit.
Roy Ken