From someone who reads these things.......
Go easy on talking about your own children unless in the context of specific learning activities you have organised. "I like helping my own children learn" is not as good as "I have used cooking as a way of teaching my child maths"
Even better - refer to anything you have done with groups of children. Did you help with a playgroup / mother and toddler group? Have you been involved with a school holiday playscheme? Organised / participated in a walking bus? Volunteered to help on school trips? Volunteered to hear children read? etc etc. These are all important and if you cannot refer to any similar experiences, it might be a good idea to get involved. (Not just so that you can put it on the statement, it's just good experience!)
Also mention anything you can do that will add to school life. Are you keen on sport? Dnce? Could you help with PE or swimming? Can you play a musical instrument? Have you done any drama or art or craft? Even cooking and gardening are useful skills in a primary school.
How IT literate are you? What applications can you use?
Look at the areas covered by the primary national curriculum (google it!) and think carefully about each one. Think what experiences or skills you have that could contribute to each area and include these.
Don't forget any previous work experience. Did you ever work behind a bar? Gives you experience of dealing with all sorts of people / difficult customers etc. Did you work on production line in a factory? Gives you patience, teaches you to be methodical and consistent etc. The most unlikely jobs give you skills that can be redeployed in teaching. It's up to you to identify them, make them sound positive.
Above all, be concrete, be specific, give examples of what you have done, be positive, be enthusiastic. Avoid the "I really want to be a teacher because I love children" (we take that for granted) and "I have 4 of my own so I know about looking after them" (Hmmm. Also may mean you will have problems coping with assignments and placements!)
Good luck - let me know if there is anything I can do to help