Well, I just did a zoom and you could do an interpretation of the cake. You could even get your DD to help out using some premade fondant and store bought decorations - not everything on that cake is gumpaste or fondant.
This is just my opinion and idea... purchase 2 rounds, Say a 10" and a 6" stacked (I like to give more room to the top of the bottom layer for surface decorations) ask them just to flat ice it - no boarders or twirlie things on it - purchase some dowells for the bottom layer and insert. Trim the 6" close to the cake and gently place it on the 10". This gives you the stacked base (I am assuming you don't have to travel with it so it makes it easier

). Then I would get a pack of the Wilton basic fondant colors for the leaves and stuff - it's like playdough really and cut out some leaves, flowers, and things like that. Any small cookie cutters would work and don't disregard other kitchen items for cutting out stuff (straws, punch circles and layer for flowers using water or piping gel for glue). If you notice on the pics, the ferns at the top are plastic as are the figures. You could easily check out Michaels for stuff like that and incorporate it.
The water is just colored piping gel - tint it blue, different hues would be good and put it in a disposible piping bag and "float" it down the front to the bottom. This stuff moves so spread it out initially with a little spatula and then pipe over it to give texture. Don't fret if the white or bottom buttercream comes through - that looks like water foam.
A plastic disp pipin bag cut like a triangle can make wavy leaves and one cut ever so slightly can give you a nice rounded shape. You could do that for the cattails and writing. The plaque - I would just do a piece of foamcore or funfoam cut into that shape and applied.
(all the non edible stuff removed of course before service)
Englarge this picture and take a look at the individual components. You can do something that is basic and gives the same idea if you start a bit early. Fondant flowers and such can be done before hand and stored in a plastic container. Your DD could help out and it may be fun for her - maybe a new hobby could be born.
Sorry so long, but you could do this - I have no doubt in my mind.

PM me if I made no sense because sometimes I ramble....