We just had our Rainbow Sparkle potion party and it couldn't have been a bigger hit!
We had 11 Girls between 6 and 10 plus 3 older brothers getting in there. There was more than enough potion mix to go around, I got the extra fiz but didn't really need it (which birthday girl loves, more for later).
It was messy but a lot of fun and poor parce-the-parcel was still sitting wrapped, long forgotten at the end of the party - the potions were better than games.
The instructions to guide you on the extras needed, suggestions on how to find them and presentation ideas was great! We used a lot of the suggestions the wooden spoons and stirrers dipped in glitter, the paint splattered table cloth (get plastic ones, there will be liquid everywhere), the nature decorations etc.
Only thing I wish I had done different was to come up with some actual recipe suggestions for the unsure where to start kids, once they got going they had just as much fun!