Lonelymum here are my suggestions, may have been mentioned on here so sorry if I'm reapeating other posts.
Use any advange card points if you ahve any from Boots, tesco, Sainsbury's cards to buy either small, inexpensive gifts (little toys, nice kiddies bubblebath, novelty shape soaps, chocolate bars or even small items of clothing like a top, socks, nice slippers etc). also, some supermarkets have a change machine where you can put all your loose change in (if you have lots lying around teh house) and out of it you get a receipt for the amount of money you put in minus some percentage that goes to some charity. the receipt can be used to pay towards purchases made in taht shop. Or, if you do have lots of change, you can put it all in individual small change bags (you'd get those from your bank), make sure you put the right amount in each of them, take them to your own bank and get the money in bigger coins or even notes, depending on how much you have. I always put small change (1p, 2p &5p coins) in a draw in the kitchen and once a year take it to the bank and it adds up to about £15-£20 a year. i know it's not much for a year but it's extra money especially when you run out of cash.
Set yourself a limit and STICK TO IT!!!! Say £20 for all the presents, then make 4 trips to the shops with only £5 in your pocket (leave your purse at home) and have a look in charity shops for good, clean toys or books, or even something like a nice little wooden chair (I saw one once for £1.50, it was adorable, rocking tiny little chair, I would ahve painted it, I just didn't buy it when I saw it and next time I went past It was sold)or a little child desk (again saw one for £3.50 once and lost it). look in shops like Woolworth or Wilkinson for paints, brushes, sticker books, little toys (for ex. Wilkinson sell a little battery operated car for £1.90 ish teh type taht turns over when it reaches an obstacle), play food sets, magnet sets etc etc.
make something yourself if you feel brave enough: a painting apron or a cooking apron that sort of thing, or nice cookies.
have a look around car boot sale, church sales, garage sales and bartgain with the seller you might end up with very good buys.
Above all keep it small, stick to the budget and think what you could make yourself.
HTH and enjoy your Christmas!