My 8 year old still night wets. She is actually having some tests done next week to make sure there is nothing physical going on with her.
She has seen several doctors & they all state the same thing....it just takes time especially those who were born premature. They all have said that you can try the alarms or waking them up at certain times but this only leads to them depending on something else to wake them up instead of learning to wake on their own.
I do not recommend stopping drinking after certain times, especially if you have a child in school all day. My daughter doesn't seem to drink as much when she is in school because she is so focused on her activities. A little water here & there plus a carton of milk at lunch is just not enough. So she drinks a lot after school to compensate & prevent dehydration.
As far as sleepovers, there are medications that doctors prescribe to use temporarily for cases such as these. They are not recommended for long term use but if a child wants to have a sleepover, most doctors will prescribe the meds. We've been offered it many times but have refused it since we don't allow our daughter to sleep over anywhere but at her Grandparents or cousins house. And her using Pull-ups there do not bother her or the family members.