I have a bit of an idea in the back of my head too... Don't know really how much food you need, besides cake. Our bday parties we have had, I really just do cake and juice, except once I did do pizza b/c the party was over lunchtime.
But. Maybe you could do your finger jello in test tubes? or cut them into test tube shapes? Love the cake, by the way. Maybe you could assign science-y names to the fruit; elements or whatever. Lay them out like a periodic table? Find the Latin names for the different fruit, maybe?
Serve lemonade in beakers? I don't know when your party is, but maybe your party place who is sending the scientist would have some science looking decor, such as graduated cups or if you have access to something like that through your or your husband's work.
“When one door of happiness closes, another opens; but often we look so long at the closed
door that we do not see the one which has been opened for us.”
Helen Keller (1880–1968)