Honestly I'd go for the SWC and save up for the BBQ next year. You'll have so much free time with the SWC, you could build your own BBQ pit.....

Is there a significant cost difference between the Zeobrite and regular sand? Can you skip the Zeobrite and get both the grill and SWC?

I run a SWC and sand filter with Al and Carl's DE "filter aid" trick. Crystal clear water and absolutely no hint of algae all season long.