Valentines day dinner and birthday cake hell(p)

G-son is turning 5 and after 3 g-kids I had managed to stay out of Chucky Cheese and didn't have to watch Barney. I felt very blessed. THEN daughters BFF took all my g-kids to Chucky Cheese on a teacher planning day. Damn her! When daughter asked him where he wanted his party it took him approximately one second to spew the words "CHUCKY CHEESE".
Due to busy weekends the party will be held on Valentines Day at Chucky Cheese.

Call to husband: "Hey your taking me to dinner on Valentines day."
Husband: "Oh, I am and where am I taking you"?
Me: With uncontrolled glee I yell "CHUCKY CHEESE"!
Husband: "What"?
Me: "You heard me"
The rest of the dialogue consisted of me explaining why.

I am also the official Ice cream birthday cake maker for all the g-kids birthdays. I enjoy it and its relatively easy thanks to Betty Crocker bake n fill pans. I've managed to decorate according to each childs wishes. But, g-son has thrown me for a small loop. Not only are we "partying" at Chucky Cheese, he wants a chocolate castle cake with cookies and cream ice cream in it, he also wants it sitting on a moat. He wants dragons and alligators and army guys and race cars on his cake. This is where you guys come in. Yeah, I'm gonna spread the love.

I bought a castle cake pan, here is my plan:
1)
Make choc. cake, make white sheet cake to hold castle and moat. I plan to firm freeze both cakes. One, to make the castle easier to decorate as it has many windows/doors and a rock wall. By making chocolate I think it will be easier to pipe around the window and door details with white icing and then use choc. icing to detail rocks. I will not put icing on the cake other than details. Is that a good thing?

2)
The moat cake, this is where I'm really boogered. After firm freezing I'm going to slice in 1/2 long ways and slice ice cream to lay between the layers. Then put back in freezer? Or should I continue to decorate (other than ornamentals)?

I thought I would buy white icing, fluff in mixer to add more air and thin down, spread on moat cake. Should I attempt to try and color the frosting with food coloring to make the "water" kinda brackish? Or should I use brown and green "dust" like stuff and feather over it like air brushing to get the "water" look?

Am I over thinking this? Am I crazy as shit trying to do this? He is very excited and has called to make sure I'm "making" his cake and each time he adds something to the mix. Are there short cuts I'm not aware of other than Publix Bakery?

I mean not only are we having Valentines day dinner at Chucky Cheese, which the husband gleefully tells everyone, BUT a castle cake on a moat, thats no Betty Crocker bake n fill I can tell you!

Please hear my call and send advice, ideas, prayers, money.....(just thought I'd throw in money)