I have seen four in one George, the two number boards and two cab lights. I agree, that's not 7 bulbs, but then we don't know the current rating of the bulbs.
You can obviously use a relay, a 5V coil relay with a small cap to reduce chatter would do the trick. With the relay, I would also use track power to eliminate any additional load on the PV.
FWIW, I use similarly rated FET parts on my Super-Chuffer and Chuff-Generator, and I've personally tested them with a 1/2 amp load without any issue of overheating. With a bad fan motor, the Super-Chuffer fan FET is actually able to shutdown the 1/2 amp switching P/S module without killing the FET, they will handle quite a bit of current. Of course, the PCB traces may be an issue as well if you put too much of a load on the PS/2 board FET outputs...