As this is in camping, I assume you're probably not going to a possible malarial area? If potential malarial, the risk is too great and I always stick to products containing DEET. As long as you follow guidelines, e.g. not over cuts/grazes, not too close to eyes & mouth, not more than recommended dosage and a thin layer), it is safe enough. For a ten month old, I'd use something with around 10% concentration. As long as a baby is over 2 months old, it should be safe.
Then, common sense approaches, like long sleeves (cool material - good for sun protection at the same time), mosquito nets etc. If you're using DEET products, don't apply that to the areas obviously covered, e.g. under vests etc - keep to exposed areas only but avoid hands.
If you want to go natural (and I only ever do this when I don't think there will be many mosquitos), products containing citronella or lemongrass repels a little. Also, avoid sweet smelling lotions, as they attract.
Hmm, just realised you've asked for insect repellent, not specifically mosquito, but the same things should apply.
Either way, take something to sooth bites with just in case. I prefer Anthisan cream (mepyramine maleate), which you can buy at Tesco etc. DEET products at most camping shops or, my personal favourite if you're in London, the Hospital for Tropical Diseases.
I hate m's with a passion - you might have guessed!