Working Resolution #3
Resolved: the United States Federal Government should increase its constructive engagement with the government of Afghanistan, Iran, Lebanon, the Palestinian Authority, and/or Syria; including offering them a trilateral security guarantee with Israel, a bilateral security guarantee and/or a substantial increase in foreign assistance.
Gramar Questions to Research:
Grammar Items 2.2
1 Semi-colon vs. dash vs. nothing vs. comma
2 And/or at the beginning – does it work with the commas
3 Them vs. those governments
You should leave the word "them" out of this. You should just say "including offering." The prior phrase "constructive engagement with" constrains the offer through the use of the word "including." Although "them" is commonly used to refer to singular subjects when trying to avoid gender-specific language, including it here (where there is no gender issue) can only confuse things.
The grammatically correct alternative to this is to say "offering the government(s)." Still messy.
Use an em-dash!
"The em dash is the mark of punctuation most of us think of when we hear the term "dash" in regard to a sentence. It is significantly longer than the hyphen.
We use the em dash to create a strong break in the structure of a sentence. Dashes can be used in pairs like parentheses—that is, to enclose a word, or a phrase, or a clause—or they can be used alone to detach one end of a sentence from the main body. Dashes are particularly useful in a sentence that is long and complex or in one that has a number of commas within it."
Source: http://www.getitwriteonline.com/archive/091502.htm
If you're going to say "them," then it would be better to use the word "government(s): before you start the list of countries.