Sizing Equipment for an Outdoor Event

Hello all, and happy holidays!

I've been hired to provide SR for an outdoor gig with a needed coverage distance 40m. I have speakers I believe will cover this with dual 15" woofers and 1" CD. Modelling suggests approximately 120dB with 500 watts at 1m. So I'd be getting peaks around 90dB even back around 40m. This is just a little show in a park. Could someone confirm that this seems suitable?

The subwoofers are the tricky part. As of now, I plan on bringing a pair of 18s. Does anyone think this is overkill? I don't want to come up short but I also don't want to lug around much gear for this one off.

The band includes the typical drums, bass, guitar, keys, vox, etc.

Any help is appreciated!