I've tried hazelnut chocolate crunch, lychee martini, orange zest. Personally like lychee martini but it's alcoholic. Think kids will like the hazelnut chocolate crunch cake.
If u're getting 2 tiers, can consider having different flavors, one for kids and the other for adults. I've ordered a 2 tier cake with 2 flavors for $112 for my kid's bday 3 years ago. U can ask pine gardens to send u the pricing, design cost will depend on the design complexity. Delivery charges used to be $15, not sure if it's still the same now.
Cheers