Call the bowling equipment manufacturer and ask them what size forklift is typically used for installation. Design the floor for that. Be sure to post the forklift load on the drawing so the contractor can be notified what size to use.
The IBC 2000 table 1607.1 point 7 lists bowling alley as 75 psf. I would guess the equipment is localized and more of a maximum. However, I do agree the forklift is the tricky scenario in this whole deal. I would hope you are using a CIP system so you could get some good load sharing properties.