Ivan,
I don't know how much experience you've got in motorhoming, so if I what I'm gonna write now is a bit on the obvious side, please excuse me. I'm just excited about getting to IRCHA.
1. Water. We're filling our water tank and water heater prior to leaving; that will give us 90 gallons. It should last until Thursday. AMA has water available and I'll let you know before you leave if water is available at site 3, else I know there's potable water at the dumping station.
2. The reason I'm filling up with water before leaving is this: Water quality. Our first time out, the water at the campground was really hard and had a lot of rust in it. So, I bought a two stage water filter (Metal Trap Ultra) that I'll be using when we refill at IRCHA. I don't know what the motor home you're bringing has with respect to filtration, but if it has a filtering system, you may want to make sure the filter(s) are in good shape prior to leaving. My wife couldn't stand the water at the campground.
3. Dumping. There is a dump station on site at AMA. We're using a chemical in our black tank called RV Digest It. It's a natural enzyme system that really works. It will also clean the level sensors inside the tank so you don't get surprised when you go to flush. We've never had a stank problem, either. It liquifies waste/toilet paper, etc., so when you dump, your tank gets really empty. I anticipate having to dump Thursday, as well. That's based on our use during the four times we've been out this year. Depending on use and your tank capacities, you'll likely have to dump only when you leave. I say likely because we don't travel any kind of distance with the black tank full.
That's about it.
Scott