Hello mate I found this so I've cut & pasted it for you .
"Loch Lomond is the largest expanse of fresh water in the UK and has the largest variety of fish in the National Park. The loch has also a very good reputation for coarse fishing. Loch Lomond has been rated as one of the hardest lochs for pike fishing. The variety of fish reaches from sea trout to chub. Loch Lomond is also home to a protected fish species: the powan (a white fish). If caught, the fish should be returned quickly to the water.
Boats can be hired from different companies around the loch such as Balmaha Boat Yard for fishing on east Loch Lomond and from Loch Lomond Boat Hire at Balloch for fishing on the south of the loch. Contact information can be found on the permits page."
Now this , on the face of it , isn't that useful except to point out that Piking is difficult there .
It's the biggest expanse of water in the uk I believe so location could be a problem and by the sounds of it you won't have much time for a look around before you fish so I suggest you embrace Google as your friend , find the nearest tackle shop to where your staying and ask there first.
Or better still give em a ring before you go .
I went there a long time ago , though not for fishing , and remember thinking to myself that it was quite open , as you would expect , choppy , and not very float fishing friendly although as I say the local tackle shop will advise best .
Sounds like a swim feeder job to me but whatever you end up doing I hope you have a great trip