Typically, such FBO's charge three fees -- ramp, handling, and parking. If all you do is pull up, unload, reload, and go (and I think your planned event would qualify as that), they charge only the ramp fee. If they provide any service at all, they charge the handling fee, but that is typically waived with some minimum fuel purchase. If you leave the plane more than some amount of time (ranging from one hour to overnight), they charge the parking fee. Where there is no handling fee, they typically waive the first night's parking fee for that minimum fuel purchase. Since this all varies some between FBO's, best way to learn what they'll charge is to call ahead.
An alternative approach is don't call, don't ask, don't wonder. Walk in, smile, say hi, be nice, do what you need, ask for help if required, smile, pack up and leave.
I do this whenever and wherever I travel. More often than not, I get few if any of the charges. If I park overnight, I pay parking. I usually get fuel everywhere I go because I like full tanks and am rarely grossed up, that generally takes care of ramp/handling fees for a day. I never opt for a hangar but can't tell you how many times I've been moved in by the line because there was space or they were 'worried'. (I really need to get a hangar sometimes when big storms are forecast - resolution for new year).
Don't get the impression I'm some slick fast talker - not the case. Ask me, you get my truth. I am usually unable to deceive or lie. Just not in me. Oh, forgot to mention that my wife is so nice and friendly I'm often just floating along in here reflected cheer.)
Flying tailwheel at bigger airports showed me how invisible I could be. They can't tow me so I have to park it. They can't tow me out so I have to go get it and I learned to just fly out from there. You'd be surprised how the towing by line people is where the fee transactions get driven from. Be extra nice to line people!
In a recent thread I mentioned that I've been using RDU for years - dropping and picking up passengers, eating & working at Crosswinds Cafe while plane watching, dropping in when I needed an approach to get home to my grass strip 10 miles away. Buying a sectional or two back in the day. Over 15 years I had never been charged a dime and never bought a drop of fuel by either FBO - Landmark, Tac Air ne Southern Jet - afterall my home tank is 10 miles away. It's not that anyone there knows me - I don't go often enough. I've borrowed a crew car once. Had line guys drive me to the terminal to pickup or drop off a passenger - always a $Fiver to the driver. However, the very last time I flew in there a month or two ago to pickup my wife, someone behind the desk ashamedly told me that they would need to charge me the ramp fee. I smiled and tried to make it easy which made it harder for the 3 women to do it but they did. Record broken!
I only call ahead somewhere to find out if they have Hertz and to reserve a car. I never ask about charges, I always ask for help with whatever. The few airports that have baggage handlers and if the baggage handlers are deployed to my little plane I tip them, but not the line guys.
There are a few airports where they always apply the charges consistently no matter what. The only one that comes to mind right now is Fayetteville NC - must be the military background. Miami - they don't know what to make of a little puddle jumper picking up a passenger - just too busy. Too busy often applies at really busy airport FBOs.
The wonderful team at Charlotte's Wilson Air Center - they do know us. They didn't care for the taildragger being dropped off at the front door and told me about it after the 5th time I did it, but now it's all red carpet, smiles and one memorable time - football tickets. I always buy the reasonably priced gas and pay to park.
I usually use KAGC in Pittsburgh - the place I learned to fly - but had the need to use KPIT a few times. I guess they don't get much casual pleasure traffic and kind of botched things by ignoring me. Thereafter they spent my visits offering discounts, extra help and extra courtesy. Thank you and I'm sorry about my ELT going off on the ramp!
This approach isn't for everyone. If you are choosing airports based on fees, calling ahead will clear things up and give you ammo for uncalled for extras. I fly to get somewhere specific and tend to pick the closest most convenient airport. The worse that can happen is being charged everything they would have charged if I called ahead but frankly it's usually better than that and if you need extra help you will often be extra surprised.
