At your Dcs age, it is easy to bulk out their presents - because let's face it, they are only interested in the unwrapping! so there are lots of cheats that I have used on my DDs.
Buy a pack of three cute vests or tops (things that you need anyway) and wrap them up individually - three presents, and they won't even notice (Last year I got night garden vests, DD was as happy unwarpping that as she was her toys!)
Any other practical presents that you need to buy between now and Christmas (or soon after) such as socks, slippers and the like can be wrapped up too. They have no idea at that age... in fact, we were always given socks and the like for christmas... in fact, I still get them to this day!
Also, multipacks of things that can be split up and wrapped up individually.
Magazines (such as teletubbies or nightgarden) make cheap but bulky presents.
Check out the £1 section in tescos - I picked up some crayons and a colouring book there a while back.
Also check out the clearance sections.
Add in some chocolate, and you're onto a winner.
Another thing we do is to make Christmas about the fun. So small presents are wrapped up into disguises, and clues are given and so you have to guess what present you have got. Usually my dad's clues are a bit bizarre, but it makes Christmas fun.
I think the presents are great, but at the same time the important thing about Christmas is spending time together as a family, enjoying each other's company and so on... that's the magic of Christmas, not the amount you spend.
Oh and for other people - get your little one to make presents to give - calendars made from hand prints etc, a small photo album made up of pics of your DC for grandma (they love that sort of thing). These things go nicely alongside your other gifts and help to keep the costs down.
HTH