Hi,
Is it Bettyglen or The village Bettyglen - they are two separate estates.
Bettyglen (old Bettyglen) is reached from the Howth Road (same entrance as Maywood). The village Bettyglen (new bettyglen) is reached from Watermill Road.
Assuming old Bettyglen, no there are not too many young couples around there. I'm from the area and the majority of people would be in their 50's/60's, its a very settled area. Having said that there is the odd house around with younger couples in it.
Lovely place to live though - plenty of bus routes and 15 mins walk from the Dart.