My son has purchased a 36 Roberts and we need to sail or motor it from Mooloolaba to Scarborough.
we have limited experience. Any advice please

Have not been round of Bribie for some years but that usually requires some local knowledge.
Could safer to go via spitfire channel and then the EK by pass channel and across after M8
Jode may have better local knowledge.

Pick your weather and you won't have a problem. Mooloolooba bar gets silted on the seaward side so give it wide berth. Watch the shipping channel along Bribie. Those big ships are faster than they look. Cross at Spitfire Channel. If you have some experience with sailing boats this is not a difficult passage.
Scrubby

No problems coming down the side of Bribie. There is plenty of water round Skirmish point at any tide. I would recommend you have the Navionics app and follow the deep water round the point. Bribie is quicker and easer than the Spitfire. Try and work an in coming tide as it will make your trip a lot quicker. You don't really want to push the tide which ever way you go. The route round Skirmish point is shown below. Don't get to close the the beach at way point one as there are a couple of lines of buoys with shark nets