To answer your last question first - I haven't worked with rayon chenille, but I have friends who make beautiful scarves and throws using rayon chenille for both warp and weft. My understanding is that you need a close sett for good results. Also, it is quite stiff when taken from the loom, but will become soft and drape well after wet finishing. The other thing I've been told is that you need to get a good tight twist on the fringe so the chenille won't start shedding with use.
There have been many projects using chenille yarn in Handwoven over the years. You can download the index for Handwoven and find quite a list of chenille projects with tips for working with the yarn. You can find sett recommendations for chenille on most of the on-line weaving yarn websites. Also, you might check Su Butler's website. She has good information on using rayon chenille.
As for the 10/2 cotton - that was related to the materials on hand and the purpose for the blanket. Baby blankets have some special considerations: 1) very short floats to keep tiny fingers from getting caught, and 2) hems or very short (1/2 inch or shorter) fringe so babies don't get it in their mouths. A hem on something with chenille warp and weft could be bulkier that you would like.
It sounds like you have a lovely project in mind. It's good to check resources so you feel comfortable and enjoy working on it.
HI Nora.....Rayon chenille makes a nice soft baby blanket. There is no reason you could not use 10/2 cotton as the warp and the rayon chenille as the weft. The cotton warp will, however, be obscured by the pile in the chenille, so the blanket will appear weft dominant. You can, however, use rayon chenille for the warp and weft in your blanket, and you would end up with a sumptuously soft blanket. Be aware that rayon chenille is heavy - i.e. a blanket could weigh as much as two pounds, so perhaps blending the chenille with another lighter fiber would be beneficial. Rayon chenille needs to be handled carefully, but I weave with it as a warp all the time. The biggest issue I hear of is people trying to weave with the tension too high, and the warp threads break. Weave with only enough tension to be able to open a shed and beat the chenille in place. You have to sett rayon chenille closer than all the charts and websites recommend. for 1300-1450 ypp chenille a minimum set of 16 epi, better if 20 epi for plain weave is what I would use. You then have to beat firmly to make sure you are getting about the same number of ppi. The chenille weaves with the CORE yarn, not the pile, so you have to sett and weave for the size of the core, which is generally about the same size as an 8/2 cotton.
The other thing to think about if you do an all chenille blanket is washability. While rayon chenille can be machine washed and dried, it needs to be done for short periods of time, low heat and gentle cycles. Lifting wet rayon chenille is the most dangerous, as wet chenille is very weak and it is possible to break threads. Instead, scoop up the wet blanket and support it from underneath when washing.
Hope that helps....