First cider - is this OK?

My son and I are making 10+ gallons of apple cider. This is our first cider but we are experienced beer brewers. Using some process info we found in Zymurgy, weheated the cider (no preservatives) to 160 degrees and added honey and some brown sugar. We cooled it to 74 degrees with a plate chiller, aerated it and then left it to coll to 66 degrees overnight. I pitched Wyeast Cider, one in each carboy the next morning. Got explosive results in 36 hours with some foam into the blowoff tubes and then a rapid falling and then disappearnace of the foam over the next 24 hours. A couple of days later a thin (1/2") layer of foam appeared in both carboys and then disappeared in 24 hrs. This has happened twice more and at 8 days in the fermenter it is still bubbling through the fermentation lock about every 2 secs.
My question is - is this normal? Everything was well sanitized and we followed our beer processes like always so I doubt we have any kind of infection. Just curious.

The fast initial ferment is fairly typical. Usually they hit a steady state after that, but variations in temp will cause the rate of ferment to vary. Sounds like things are fine.

How much brown sugar and honey? I've never had a blow off on cider.

Otherwise it seems right.

We had 4 jars of honey and a few pounds of brown sugar left over from a previous brew weekend plus the label on the cider showed 30 grams of sugar per 8 ounces of cider.

Assuming the jars are the normal 2 lb jars, and by 'a few' you mean more than 2 but less than 6 lbs of brown sugar, that's a pretty healthy addition of fermentables. Did you check the OG? It'll be alright, I would guess, but you might have to let it sit awhile in the bottle to mellow out.