I suggest you go pick up a Black n Decker VEC1093DBD 40 AMp smart mode portable battery charger. This will re-charge your two batteries to their 90% charge state in as little as three hours time if discharged down to around 50% charge.
I have NOT had any luck trying to get a WFCO 8900 series converter charger to ever go into BULK CHARGE mode no matter what I tried to do.
Since you could not get it done from your test run at the house there will be no way you will get it done at your FEST LOCATION.
To re-charge your batteries I think you must come with 14.4VDC with a capacity of around 40AMPS to quickly re-charge your two deep cycle batteries.
About the only place that can get a you something like the VEC1093DBD charger by next Tuesday might be AMAZON with their two day service.
You may be able to connect a single DEEP CYCLE Battery to your TRUCK BATTERY terminals using jumper cables and run your truck for a few hours.
If you can't locate a VEC1093DBD then purchase the PD9260C Smart Mode Converter/charger for about the same price and use that as a portable hookup.
Maybe others on here will know a trick -
Roy Ken
