Yes, it's absolutely fine. The dynamo output is more than capable, and as I discovered at the M-G club Scottish rally last year, you can even not get around to fitting a relay
and leave them switched on for 12 hours without the battery going flat (if you have the stock sized battery, which is OTT to allow for radios and such). Obviously, fitting a relay off the ignition is the way to go....
The dynamo is rated at 14V/11A by the way, so nominally 154W.
You should be able to hold a load of 120W total quite happily, without battery discharge, which is more than sufficient for lights and grips.