Good wedding ettiquete?

i am not sure if i spelled ettiquete correctly - anyway, a very very good friend of mines little sister is getting married. Last year, i was of course, invited to my friends wedding, and i had her alterations for her gown done by a seamstress friend of mine. and her mother was so greatful because it saved them a lot of money. this year, he rlittle sister is getting married, whom i am not close with, but my friend, when planning the bridal shower, asked me if i knew someone at this place they wanted to have it - turns out, i had managed at this restaurant years ago and knew the banquet manager very well, and was able to get them a fantastic deal on the shower, and, am getting several of the bridesmaids gowns altered again for an awesome price - also, i stepped in during the bridal shower when some of the bridesmaids (his side that we dont like.. lol) just sat there, and kept the whole thing moving, doing what they should have been re: present opening, organization, set up and yadda yadda... so of course, everyone is incredibly greatful for the help i have given them over the last 2 years worth of weddings, and now, i am invited to the little sisters wedding.. while., yes, i believe it was good form to invite me, but my question is, should i go??? because i am only invited because if the help i was able to give her sister (my friend) and her family...