You may want to investigate Hard Dollar.
You will encounter some difficulties in trying to merge field management, with estimating, with accounting. All three have very different needs and philosophies. You will have to decide what you want the software to be really good at, and for what you want it to be adequate.
Another thing to remember, IMO, is not to let accounting drive the bus. Accounting deals with the money that the estimating and operations groups make. You may want to split out the accounting from the other functions.
I work for a general engineering contractor and we switched to Hard Dollar a couple of years ago and are currently in the process of upgrading our accounting and PM software. We are switching to Viewpoint. The estimating software can export data to the accounting package but we are choosing not to. I have found that these kinds of interfaces fall apart at the "quantum" level. That is to say, that the level of detail is immense and its the details that muck things up. Lots of vendors these days are promoting their "total package integration." I'd be wary and insist on some real world demonstrations where you try your hardest to make it not work. If you can't make it fall apart, then you've found yourself a good product.
From what I've seen the three main estimating packages out there for your type of work are: Hard Dollar, HCSS, and Bid2Win. I've used all three and they are all good. There are others I'm sure.
Accounting packages for earthwork guys would be Viewpoint, Maxwell, and Explorer. There are others but they are the ones that made our short list.
I've never been particularly impressed with Timberline accounting or estimating. It is tailored for general building construction and we found it limiting. The building guys love it though.
Hope this helps. Good luck.