Welcome over to Hiking with Kids. Like I said over in the Register I have twin 6 year old twin girls. My girls have some learning delays and sensory issues. One of them occasionally is freaked by a campfire. Then the next night she's right there with cooking smores. To date we have only car camped. We started when they were 16 months old.
In the past we have done "hikes" going on trails that we could bring our Cougar side by side stroller with the jogging wheel on. It was good for them having a familiar place that protected them if they wanted. It got the family out on the trail and we had several nice picnics in a pretty clearing in the woods. For the last year we have been doing short day hikes. We are cautious to not have hiking be a bad experience. Push a kid too far and it gets ugly for everyone.
If you are going with young twins I think you pretty much have to also have two adults capable of carrying a twin each. Pretty much guaranteed to happen. Mine are identical so they hit the limit at the same time usually. Sometime after having a juice box they will also both have to pee at the same time.
One big issue here in NE USA are Lyme ticks. It's a whole big topic in itself about how to deal with but we check the girls when they get off the trail and again in the next day minimally. It's bending the truth a bit but we tell them we are checking them for bug bites. If we were truly honest and told them we were looking for ticks on them one of my twins might never go outside again.
BTW if you haven't already, read the Hiking with kids FAQ in this section. Great info there.