There aren't any 'jump off' sites at Opeongo, no. There are 2-3 sites within spitting distance of the put-in however. I don't imagine they're heavily used except by people doing the same thing you are.

Or you could just camp on the grass at the access point and let them know in the morning to charge you for an extra night. No fires. I did this myself in June and it's fine - just let the permit office know so you can be charged accordingly, the permit office staff said it happens all the time. Have your stuff packed up before daybreak. I wouldn't waste my money or time on anything frontcountry, not when there is a perfect spot for your tent. Just watch out for geese poop... LOTS of geese poop.

I've also camped at the costello creek picnic area when I arrived at 1:30am.. was packed up by 6am but still let the permit office know so they could charge me for the extra night. 12 bucks is better than 45.

As soon as you turn  left off HWY 60 to Opeongo Road, it's on your left, maybe a few hundred meters up the road. Its marked on Jeff's Map as a tiny loop in the road, just opposite Costello lake (which is on the right of Opeongo Road). Have fun man!

Just wanted to post about what we ended up doing for our late arrival to opeongo access point.  Thank you to all for your suggestions.

I had settled on the Costello creek picnic area however on arrival my girlfriend was apprehensive to camp there due to the proximity of the garbage bins.   We ended up pitching our tent in the upper parking lot at the access point (they is a patch of grass at the east end of both the upper and lower parking lots) in the morning I went down to pick up my permit and let the mnr staff member know we had camped out in the parking lot....they told me they wouldn't bother to charge me the extra night. (Right on! Free night in the park!). If anyone runs into the same issue just know that there are places to pitch a tent at the opeongo access point (even places free of goose poop ......peek lol!)

Ken