Coliseum and Burwell are quite fun and offer some easy sub-alpine rambling and minor areas to scramble. Or you could head up to the Crest Trail from any of the TH's - can find anything from easy hiking to difficult scrambling if you are looking and get some views to boot (for example, the peaks between the Lions and Magnesia Meadows have a well marked trail, but it still has a scrambling feel, has a section with a bolted cable which could give you a bit of taste for some exposure.)
I think I would start by driving up Seymour and heading for the 3rd peak - nice and short hike in, well marked, lots of people around, not to difficult, nice views and options for other things to fill out the day.
Other areas around DT Vancouver offer just as easy access and an array of similiarily introductory style trips: Golden Ears is a popular trail and has a few scrambly sections near the end; there are similar objectives in Chilliwack Valley that would be good for a beginner.
Goodluck and be safe!