Concerned If It Rains, What Are Game Ideas for a 5 Yr Old Party?

When you say water slide rental, I'm envisioning one of those huge inflated /blow-up type slides with a mini-built in pool...so bear with me if you're actually getting something more substantial, that will be set up next to an actual full-sized pool. That said, I can't think of a good backup plan. Whether this were going to take place in your own yard or a nearby park, there are way too many people (kids) to transport to a nearby restaurant if your home is too small to host a large crowd and there are definitely going to be way too many parents to work out a plan with fast enough in order to change gears at the last minute.

If you can't host people in your house, I don't see you being able to get all 30 guests to a nearby restaurant like a pizza or ice cream parlour for instance or an indoor gym like Sky Zone or Gymboree without reservations well in advance.

If you haven't sent out invites yet, maybe consider downsizing the guest list to no more than 10 -15 kids...and that's still alot of little ones IMO, but problem solved- you'd more than likely be able to host them in your home or if necessary could POSSIBLY get into a restaurant or gym without reservations.

However, if this IS indeed something that you're setting up right on your lawn at home, you could always rent a party tent and have the food and games in there rain or shine so you don't waste money, or if your house is big enough to accommodate that many people relax and play games eat and call it good. I'm a big fan of the following book for party game ideas (for both indoors and out) for kids (especially large groups of kids):

http://www.amazon.com/Great-Big-Book-Childrens-Games/dp/0...

On a side note, not trying to be snarky, but with that many young kids (many who may not swim well or at all) and a water activity planned, I hope you have enlisted the help of a few trusty adults who will give their full undivided attention and act as water safety guards. Floatation vests should be a required MUST if this will be a slide used with a full-sized pool. So many young and unpredictible kids and water...seems ripe for something to go wrong..even if this slide has pool section that is fairly shallow there could be trouble and/or danger with that many kids. JMO

All I can say is it sounds like you're going to have your hands full. Whatever you do, talk to your insurance agent to make sure your homeowners insurance will cover you if there is an accident with the slide. Those inflatable slides are notorious for serious and deadly accidents (mostly kids/people getting paralyzed if they go down the wrong way or crushed if they're not secured properly or deflate.) See: http://www.rideaccidents.com/inflatables.html

Maybe hire a party planner instead. Let the planning be their headache! LOL

FIRST: Way too many children for a five year old's party.

A simple picnic in a local park would be great for kids that age.

If you must be inside due weather and can reduce the invitation list, you could have a pizza/hamburger/picnic party at home. Kid's that age do not necessarily need games....give them a few toys or a video, some food,cake and goodie bags and they will be fine.

Parties for children this age should not last for a long time.

That's alot of kids! I remember having just 10 kids and about 25 adults for my kids and having it be done in 2-4 hrs depending on the venue or locale. If it rains and you have a water slide, couldn't they still go out in it? Assuming there is no thunder and lightning of course. At the age of 5 usually a venue birthday is best, like Chucky Cheese, your local Zoo or aquarium. Little ones love that stuff and you get to enjoy the party rather than run it.