Hi, it is a bit of a shock - and upsetting - at first, but thankfully there's no way near as much stigma attached to wearing glasses as there was when I was young (am 43, started wearing them at about 13?)
DS was diagnosed with a squint (very obviously, literally appeared overnight) when he was 2.1yrs. We did have a bit of a battle getting him to wear them (only took 2 weeks but felt like forever) but that was probably more due to his age. DH was particularly upset - even though he wears glasses and I wear contacts/glasses. Now he can put them on himself, likes wearing them, has 2 pairs to choose from each day, and, most importantly, now seems to recognise that they make a difference to his sight
A few of DD's friends (she's 5.5) have glasses and all started wearing them fulltime from day 1 - no hassle/bullying whatsoever, I think they're deemed to pretty cool now Like you, they chose their own (Bratz, Barbie etc ) which really helped.
I wore my glasses a lot more when DS started and when one of DD's best friends started wearing theirs - that helped too. Do you or anyone else wear them?
Re patches, DS was supposed to start wearing one in the summer. We never actually managed to get him to keep one on (again more age related I reckon) but fortunately when we saw the orthoptist 5 weeks later he didn't need one - the glasses are correcting the squint on their own, for the time being at least. If your DD does need a patch, she won't wear one for more than about 2 hours per day. Any longer than that and the good eye would be affected. We were also told that we could split that into 2 x 1hr each day if it was easier.
Again, a girl in DD's class has a patch, wears it at school til morning break, no hassles. I think you can rationalise with a 5 year old about the importance of wearing one if needed. You can get nice patterned ones, so again they can choose one each day.
HTH, feel free to ask any more questions