If you are healthy you will probably be fine, maybe tired following the flush but OK. When I started I was very ill with candida and barely out of bed so they really exhausted me.
It's good to have some Emergen-C available and take a couple packets after flushing to help restore electrolytes. You can get this at Wal-mart now.
Just don't plan any strenuous activity for that weekend just in case it tires you some.