I've got 31 days....

SOS...SOS....My parents 50th wedding anniversary is the end of May and guess who's back yard they have decided to have the party in?? Well, I DID say I would help in any way. Of course I was thinking getting the balloons, arranging some little sandwiches, tea and coffee etc. I was not thinking Hostess with the Mostess.
We bought our house 5 years ago from a sweet little retired (note retired) dutch couple who had all the time in the world to putter in their extensive gardens. And, I might add, they were darn good at it. How very fortunate for us to inherit such lovely gardens. How very unfortunate for the gardens to inherit us. There are perennials in abundance coming up who knows where and I-don't-know-when. There is a lovely little pond in the middle that in my memory was a show-stopper when we looked at the house. There was a lovely little fountain in there and real goldfish! Now, after 5 years, frumpy is the word I would use to describe it. And to top it all off, our Amelia-Bedelia loves to do laps around and around the pond effectively destroying all grass and leaving lots of space for the weeds to move in.
So, in a desperate attempt to make this backyard worthy of a 50th wedding anniversary, there I was last night in the pouring rain clipping the rosebushes (I hope you are supposed to do that) and spreading grass seed around followed by topping it with fresh soil - I've seen other people do this so I think this is what you do. HELP - I am not a gardener. I'm open to any suggestions short of moving out and giving the gardens a break. Please people....I've got 31 days...