For well priced accommodation check out www.needitnow.com.au
and anywhere they suggest in Perth will be pretty good. For B&B or guest house accommodation expect to pay a bit more but if you do a google search on accommodation, perth, wa you will find heaps of sites to choose from with a wide range of accommodation choices and for different budgets.
As for what to see and do since you will be riding into Perth in the afternoon of the 1st and flying out on the 5th that gives you 3 full days. I would reccomend a day around Fremantle which is the port city and lunch at Little Creatures by the wharf. Check out www.fremantlewa.com.au
for things to see and do there.
Day 2 I would go to Rottnest Island. A beautiful spot, llovely bays and beaches and a delightful ride around quiet roads around the island. You can take your own bike on the ferry over there. The ferry trip takes about an hour each way.
Day 3 would be good for a river cruise on the Swan River that would also take in a couple of wineries or if not the cruise then a half or full day tour of the Swan Valley which is a major wine district about 40 minutes drive from Perth and there are plenty of tour operators.
If Michelle and I can arrange it we will try and take a day off work one of those days to show you around and maybe have dinner that evening, if that fits in with your plans.
Cheers, Shell and John