I apologize that no one has responded to your question sooner. Different experts come online at various times. I just came online and saw your question. My name is ***** ***** I’m a biologist with a special interest in trees. I'm sorry to hear of this incident. I suspect the reason no one has responded is that putting a value on a tree is complicated, and is nearly impossible for someone who isn't there. However, I will give you some information that will help as much as possible under the circumstances.
The following site has all he information you would need to compute this for yourself, except that you'd still need a price from a local nursery on the largest oak they would be able to sell. I don't think either your or an online opinion would carry much weight with an insurance company or a court. However, if you're dealing with a company who will accept your appraisal, this website would be a solution for you.
If you need this information for an insurance company, you'll need to get an appraisal from a certified arborist. A certified arborist who can actually see the tree is considered the expert for such a case. This link will take you to a directory of certified arborists so you can find the nearest one:
I hope you'll get a substantial amount for your trees, even though you can't replace trees of such stature. If you need anything else, or if you need help with the formulas, just click on REPLY.
My goal is to provide you with excellent service – if you feel you have gotten anything less, please reply back, I am happy to address follow-up questions. Please remember to rate my service only after you have all the information you need. Thank you!