If it's just for some fun jamming then it doesn't have to be strictly traditional bluegrass and some fun can be had with the basslines. Given that they aren't using traditional instruments then I see no reason for you to. Ignoring the boring regimented parameters of genres take a look at Bela Fleck & The Flecktones (what's known as 'New Grass' I think) and Victor Wooten is happy playing funky basslines on a far from traditional electric bass, and God only has knows what 'Future Man', Wooten's brother, is playing, a Synthaxedrumitar if memory serves.
It has the traditionalists running for the mountains, oh hang on, they're already up there. 😉