well I am going to guess the charges will NOT be up to you, but rather what the local authorities feel is possible to charge with and be able to prove that things happened
and this also is nothing new, , I have on MANY occasions caught father and sons, and even grandfather, son and grand son ALL trespassing at same time before
its why I always say its a generation thing, taught by parents, that so many trespass here in PA and feel its there RIGHT to do so, as that is what the parents always tell me when I catch them that its THERE RIGHT to do as they please cause they LIVE THERE or near by and that some how means to them its there RIGHT to go where ever they feel!.
any how, as for your issue
I am going to maybe sound like a jerk here, but don;t mean to! just saying what I see in your pic's
but, for one, I am guessing your SIGNS were stolen, but I have to ask, are they 100% on your property, or the road right a way, as some what look to me they might be on the road right a way, making any issue's with them be not possible!
next, do you have any actual pictures or videos of them actually in possession of the signs?
YES I know its trivial, but when things go to court this can be brought up!( I am currently in a theft case with mail thief ad it is part of the case, I have both pictures and vid and eye witnessed the theft and put together a case, of capturing the last 11 days in a row stealing things and setting up a sting operation in my driveway! and its still not a sure deal I am told? GO figure, criminals have more rights than honest folks at times, and since this was MAIL being stolen, , and supposed to be a FEDERAL case, due to lack of care by Post office and Fed, they are passing it down to local courts)
Over the yrs I have taken many trespassers to court, and its NEVER easy, so, heads up
if any of these folks admit to the crime, get it on recording before getting the law evolved is, my suggestion, video confession even better!
fro,m there talk to local law , and ask then what all they can do for you! and do ALL they can!
might end up costing you time and even MONEY to do so, but it does send a message if you are ina smaller town where rumors fly and travel far and fast!