G'day,
How many channels does your mixer have?

I think with 4 tracks I would use as many mikes as possible to record the group & much closer than 5m. SM58s work better close up I think. They're pretty common so you might be able to borrow more for the occasion. I'm assuming your mixer can handle this (another loan?) Mix down to stereo, experimenting with the mix before making your final recordings. This will account for 2 tracks.

For good ambience I think you should record the distant stuff in stereo - another 2 mikes, possibly not the best two. There's the other 2 tracks.

If you have reverb you'll probably want either the recorded ambience or the reverb but not both, I think that might muddy the sound.

Cheers,
Alan