Do you and your DH want a double sleeping bag?
For me, I like a square-ended , or 'envelope' bag, not a mummy or cocoon shape - I like as much space as possible. Also, I would avoid anything with a nylon / shiny lining - go for cotton, or 'soft touch'.
I find the Vango 2 season bags plenty warm enough in the UK spring, summer and early autumn, but loads of people seems to want something warmer. For me the Vango Harmony Grande is an ideal bag for an adult - with a fleece blanket to put on top if it is cold. The Vango Ambience has a much lower 'ideal' temperature for use, and has an optional zip-on duvet so that you can make it 2 or 3 season.So warmer - and mre expensive.
You want zip baffles - nothing worse than feeling the cold zip against you - and having a draft come in through the zip.
For your 6 year old -the same thing - DS had a 'Junior' bag, but you can just fold the end under.
If you have a Blacks near you they have loads on display and the staff are very knowledgeable.
Buy a quality brand - don't get one from Halfords etc.