关于dress up这个用法

关于dress up这个用法
例1.Last Christmas,the circus owner,Jimmy Gates,decided to take some presents to a children's hospital.Dressed up as Father Christmas and accompanied by a 'guard of honour' of six pretty girls,he set off down the main street of the city riding a baby elephant called Jumbo.
2.She was dressed up in her Sunday best.
3.After having decided to take some presents to a children's hospital,the circus owner,Jimmy Gates dressed up as Father Christmas and set off down the main street of the city riding an elephant called Jumbo.
4.He was going to lend me a policeman's uniform so that I could dress up for the party.
我想问的是dress up不是应该要用被动语态的吗?为什么例3,4直接用主动语态的呢?为什么例1,2就用被动?请问例34有错吗?例134都是出自于新概念英语2册第65课,两种用法都对吗?请讲解一下个中原因,
例3可否改成After having decided to take some presents to a children's hospital,the circus owner,Jimmy Gates was dressed up as Father Christmas.He set off down the main street of the city riding an elephant called Jumbo.
例4可否改成He was going to lend me a policeman's uniform so that I could be dressed up for the party.