I need help!

So, our party is at the end of January, with 25 people max (kids and adults included) at a children's museum. Our invites stated "free full day admission for 1 kid + 1 adult". So would be roughly 10-11 kids + their guardian. I have 3 questions for you party experts:

1. RSVPs: we are inviting friends from daycare. We have heard back from most people on RSVPs except two. The problem is, I do not have their parents' contact information at all! I have emailed our daycare director and I have asked her to forward my RSVP reminder message out to these two families on Friday, but I still haven't heard back. The thing is, I do need to hear back because if they are not going, I want to send invites to other people!

So my question is: What do you do when someone doesn't RSVP, and that you do not have their contact information to check with them?

2. How much pizza should we order? For 25 people at first we thought about 5 pizzas, but then today we just came back from a friend's party and they only had 3 medium pizzas and each person got barely 1 tiny slice. We got home and eat instant noodles. But is 5 pizzas too much? How mufh food should we order for approx 25 people? (There is a possibility siblings and spouses may come. Possibility)

3. How much cake do we order????? This is making me scratching my head! We are planning to order from this very delicious cupcake place, but their regular cupcakes are gigantic. $35 @ dozen. They do have a mini version, $18 @ dozen, but they are quite small... maybe 2.5 of the minis = 1 regular size cupcake. They would be OK with little 3 year olds though. The regular ones are really too big for small kids. At first I thought about doing just 2 dozens of the regular (around $75-80 total?), but after we got back from a friend's party, their cake, which was shared for the whole room, was probably about a dozen of the big cupcakes. But then you can't ask people to "share" cupcakes! Now I am thinking we should do 1 dozen regular and 1 dozen small ($60 total). But when there is a lot of small cakes it would look weird visually.

How much should I order?

(This is the place we are going to be ordering from: camicakes.com - in case you are curious to know what they look like)