KatyW - not sure how big your family is, but we went to a lovely little cottage in Mousehole, Cornwall last September - only sleeps three though (one double, one single room). Very reasonably priced. Beautiful little village with a couple of pubs, few good cafes, few shops and lovely harbour. Not much parking in the village, so you're given a permit for the harbour car park, which is about 1 minute away from the cottage - no problems for us with buggy. Right next door to fantastic restaurant - and the baby monitor range stretched easily! Hence we sat celebrating our anniversary, eating our first meal out for eons, sipping champagne, and watching the monitor!! Bliss
Very small beach attached to harbour - ideal for little ones, but beaches at Newlyn and Penzance only short walk away. If you want to get in tha car, some superb beaches close by. Lots of good walks too.
If you have a toddler tho', you'd need a portable stairgate, as the property has stairs. If you want details etc, let me know...