OK my opinion on this is this;
why do you think you are not good enough to do this yet? Get a pattern for a washcloth that includes an intarsia logo or fair isle logo on it. Something small. Play with it and see how you go. You can do the knit stitch and the purl stitch right? Thats all you need! I have never done intarsia and up until recently I'd never even done socks.
Basically I started knitting when I was a kid. At 19 I made a short sleeve sweater - it was too small so I had to make it again in a bigger size. I then didn't knit again for 20 years. In March I made a scarf for my mother for mothers day. In June I took the plunge and decided to do a real challenge. I knit a sweater in the round from Big Girl Knits book with a time limit of one month for the Knitting World Cup. It consisted of knit stitches and purl stitches and following a pattern.
After this, I made a sock on DPN. Then I started another sock on DPN. That sock is still a work in progress but I then discovered the two circs method of socks and I've made two pairs of socks since then! Socks are one of the hardest things to knit IMO but once I tried to make one and saw how it works then it becomes easier.
For doing intarsia or colour work to learn how to follow a chart before doing the colours, I'd make a wash cloth with a logo on it - Rebecca has some nice ones on her blog.. http://whimsicalknitting.blogspot.com/ this will give you an idea of how to follow charting. Although Rebecca's cloths don't have charts - the pattern is written out in full. You can find other patterns for this kind of "logo" knitting that do have charts instead of writing the pattern out to the full - depends how your pattern is for the childs sweater.
In addition - we are all here to help with your project - when you get stuck post pics and talk to us to tell us what you are stuck on. You'll get an ocean of help from some wonderful very experienced knitters here.
At the end of the project, you'll feel proud and you will have accomplished something really great. Don't let the thought that you can't do this get in the way of the fact that you can do this.
Failing that if you really want to pay someone to knit it for you - you'll be looking at the cost of the yarn (and pattern) as you know and then likely to be an hourly rate. What is someone worth per hour? How often do you sit and knit and when you do catch that precious time to be able to do knitting how much would that time be worth to you?
It is all rather relative, and very much "how long is a piece of string" - personally for me to sit and knit is so hard right now that the time I spend knitting is very precious - if I were to give that time over to someone to knit something 'commercially' I'd probably right now be suggesting a fee of around $100 an hour (£50) because the time is so precious to me right now.