The background: My FFIL, 2 of his siblings, my matron of honor, and one of my father's cousins are diabetic. At our reception we are having both a wedding cake and a grooms cake, but unfortunately the bakery we're using (as well as the other bakeries we looked at) don't offer sugar-free cakes. Our venue's catering department said that they can make a sugar free dessert table to accommodate them.
My question: We can't decide HOW many desserts to have - my FI would like 2 or 3 options since, in his words, his "dad is spending all this money (our parents are splitting the cost of the wedding) and even though he can't eat the cake, I want him to be able to have whatever he wants and enjoy himself and not have to worry about being denied dessert cause it's not sugar-free." 
Etiquette-wise, do we need to have enough for ALL 200 guests, or just the 4 or 5 guests that can't eat sugar for medical reasons.  If we have it for all the guests, then that's going to be a lot of extra money, but if we have only enough for the guests who can't eat cake, my FI is worried that if there is a table set up, other guests will take the dessert before his dad and our family members can get to it. 
Can we get a small amount and have a couple options plated together and have those desserts brought specifically to their seats?
I'm not asking this from the "I don't want to spend more money on my guests" approach, but if I can avoid having to order an entire dessert table to feed 200 people, when there already will be more than enough cake (which would be plated and served with a chocolate covered strawberry and chocolate mousse served in one of those edible chocolate cups) so there won't be a surplus/wasted food, and not have my FI worry about whether the sugar-free food is getting eaten by the regular people instead of who we're really having it for? 
Thoughts/ideas? Thanks! 
