If you feel you want to cancel it because of lack of people, thats fine. I understand how you can feel with people not coming and all. I was one of thoses people that didn't show up last time. Even thought I was heading that way, till something happened on the way up. (Long bad story) :( I felt bad I didn't make it, but there was nothing I could do.
Maybe just Pm people and if they can't say for sure that they are coming, then don't plan for them. Just tell them they are more then welcome to show up, but to bring their own supplies. I sure they will understand if you tell them, that you can't supply things on a maybe. It's just like any other party, you plan for those that accepted only.
Please, What even you decide, just let me know. If you want it to be just you 3 or if you still want to give it a try.
Try not to stress about the whole thing, no matter what I'm sure you will have a fun time, even if it's just you 3.
Oh also if you still are going through with it, I MIGHT be bring a friend and her dog with me. I'm never sure about her till the last minute, so don't plan a thing for her, I'll take care of her if she comes. If you don't mind her coming.