While I don't ave any specific hotels or resort to recommend that would have lots of single parents, I have always felt very welcome and at ease in all the family resorts and holidays I have been to. Other families (with two parents) generally don't care and in fact tend to invite you to join them for say lunch or dinner so you have adult company: a great way to make new friends. In no particular order, I can recommend
Neilson Holidays and
Club Med. If you fancy adventure-type holidays,
Exodus and
Intrepid Travel do some really well organised family tours - and other families have always been always lovely. Whatever you choose, have a great time with your children.