My advice would be to get the weights of your passengers, then fill out the weight and balance calculations for a few aircraft.
Also, I would not listen to miroc. Risking the lives of his wife and daughter because its not legal but "technically" OK. The only thing he said that was useful was that you are not a test pilot. Apparently he is and his family members are test passengers...
pboyall makes a good point too, I would estimate that you have probably about a 20% chance of the day you plan to go actually working out weather wise.
If you want, I will take your girlfriend and you can take her parents. Hopefully that will ease any worries about W&B.
