The price for the hotel shuttle to go back to the airport is an outrageous rip off.
Do not pay this outrageous shuttle fee for such a crappy service.

Use the "Frankfurt am Main - Gateway Gardens" train station where S-bahn line numbers "S8" and "S9" will take you to the airport terminal 1 in only 1 stop for 2.10 euro each way.
The train station is only a 5 min walk away from the hotel on totally flat sidewalks.
To get there go past the main entrance of the Holiday Inn hotel and walk past it.
Keep following the road as it curves right.
There is a grey building with red window frames very close to the train station.
The train station has both escalators and a elevator.

If you use the train to ARRIVE to the hotel from the airport, then again take S-bahn line numbers "S8" and "S9" from the airport and get off after 1 stop at "Frankfurt am Main - Gateway Gardens" station.
Once on the platform, you can either use the elevator in the center of the platform to exit or the escalators on either end.
The escalator exit/entrance closest to the Hampton is called ""Bessie-Coleman-strasse".
Once outside, walk in the direction of the grey building with red frames and go past it and follow the road as it curves left.
First you will see the holiday inn hotel on the right side of the street, go past this and the Hampton is around the corner on the right.

To buy the 2.10 euro tickets (price for one way in both directions) select "kurzstrecke" (short journey) on the machine.
The ticket machines at the airport and near the hotel all take all credit cards.

Remember the frankfurt airport train station is at terminal 1, so whether you take the 2.10 euro train or overpriced rip off hotel shuttle, you will always have to take another (fortunately free) bus to go between terminals 1 and 2 (or vice versa).