hi! i am making a surprise dinner for my family, and i need some help. i am 13 just learning how to cook well, and i am making this recipe i have that is some kind of spaghetti and mashed potato s on the side. i am cooking for 4 people including myself, and i don't know how many potato s i should make...and we are a potato loving family! and i need an idea for a drink but please no alcohol, just like a nice drink to go with it all! thanks! and also, how long should the number of potato s cook?? thanks!