J.B.
What I did when figuring this out was that I first downloaded all of my claims from the prior year from my old HMO provider because I had no idea whatsoever what things cost because I always just had my co-pay and that was that. Some things shocked me - a 10 minute trip to the pediatrician for a wart to be frozen was $340. Routine bloodwork was hundreds of dollars. A visit to an ophthalmologist was $700. Allergy testing was $1200. Generic ADHD meds are $200-300 a month depending on the type. My husband met with an endocronologist - the office visit and blood work were $4000!
From there, I plugged in the deductibles, the premiums, what I paid for pharmacy and co-pays on my old plan, and the out of pocket max to find out which plan would end up costing us less. I went with a plan that has a $2500 deductible per family with a $6000 out of pocket max for in-network providers. That way even if we reach the out of pocket max, my total spending including premiums is about $8000 while on my old HMO, the premiums were much higher so once I combined those with my co-pays and occasional pharmacy expenses, I realized I was paying almost $10K a year for health coverage, to the high-deductible plan was the better buy.
It would be hard to give you advice without specifics, so see what you can download for claim history from your old provider so that you give yourselves real numbers to work with. Honestly it doesn't make sense to me that you would risk increasing your costs by $5K per year to save $1800 in premiums but I'm assuming that you would reach the $10K anyway and really, you'll only know that by actually looking at your claim history. Most of us in my family typically have only routine well visits and no one has any chronic physical health issues that are being treated, but things like getting an x-ray done to make sure that that swollen ankle your kid has is just a sprain and not a break or getting a wart or mole removed or having your doctor "run some tests" just to make sure a mild symptom isn't something more serious can add up quickly. We ran up almost $15K in claims last year, which is way more than I would have guessed.
ETA: Yes on the health savings account (HSA) for your deductible. If you go with the lower deductible, you would be able to save that entire amount in your HSA (the limit per family is $5-$6K I forget the exact amount). If you get the higher deductible, you would have to save that money elsewhere in case you ever did need to cover expenses that high. If you go with an HSA, it's another reason to have an accurate look at your claim history so that you don't opt to save too much (which can be forfeited if not spent) or too little (which may leave you without enough to cover your costs and make you lose out on tax advantages).
ETA in case anyone is still reading this - I agree with Jo that figuring out what you would actually be charged vs. what they would have billed your prior insurance company has no rhyme or reason. I tried to get some basic info from our regular docs (pediatrician and primary care) when evaluating our options and even they couldn't tell me what the contracted rate for a visit outside of well visit (which is covered 100% anyway) would be because it's different from carrier to carrier. Usually what you would charged under a HDHP is lower than the rate they would contract with an HMO but not always. It's also hard to predict expenses under these plans even when you enroll. My son needed a more detailed vision workup this year than what he would have gotten at an optomotrist so I took him to the pediatric opthamologist we've used for one of our other kids. I asked in advance what the charge would be and they said "somewhere between $300 and $700 we won't know until we bill your insurance." WTH? I figured it would be on the lower end because I knew they billed the HMO $700 and this one came in at $750 or something. It's maddening.