I think the perfect app for you might be MeContacts, it gives you a page of tiles, each tile being a contact. It then gives you a function to group SMS. You can have a number of pages so Syndicate, Family, Friends, Work etc. Takes a bit of setting up but its pretty cool once done.
I also use Handcent SMS which gives you your contacts as a tick list so a bit easier to select multiples. You must make sure that your contact is marked as mobile in the drop down next to their number on their contact page. If that box says home or work it won't recognise it as an sms number.
A word of caution, I have seen reported that people have had problems with sending large texts to large groups... only the first few get them. I have no idea why but wonder if it is something to do with memory. So the first time you try it just be aware and check that everyone got what they were supposed to.
To forward a text you just need to long press on the body of the text and you should be given a pop up one of which will be forward.
Hope that helps.
