I can't particularly speak from the scouting aspect of it, however, I feel relatively comfortable speaking about the various tablet options you have at the moment. For a cost effective solution, I'd certainly recommend looking at purchasing an Android tablet - both Windows (surface), and Apple (iPad series) tablets are much too expensive for this purpose, and neither offer low cost solutions.
In the sub 100 range, you're looking at the following tablets:
http://www.amazon.com/gp/feature.htm...cId=1000978251
Again, I can't particularly speak for any of the given tablets, but what I can recommend is that you try to find something larger than 7 inches if possible. The extra screen real estate will be very valuable if you develop your own scouting application, or if you try to use a web app of some sort.
By the way, make sure you're not getting something like a Kindle Fire - get something with a stock android version, which makes it much easier to add your own apps. If I had to pick any particular brands from there, Acer and Dell tend to produce decent quality tablets at a low cost. Samsung tends to be a little pricier (may not fit into your budget), but the Galaxy Tab series is well known. I know Lenovo makes decent, well built laptops, but I can't speak for their tablets.
Now, as for developing for the tablets - as long as they're all running the same Android version (roughly), and they're all at the same screen size (again, roughly), you don't really need to worry about compatibility. You'll be able to make components display relative to each other, with the spacing scaling automatically as necessary. The difference comes when you've got different android versions (i.e. 2.3 vs 4.4) and different screen sizes (i.e. Nexus 4 vs Nexus 10), because if you use software developed for a 4" screen you'll either have blurry images or a lot of dead space in the 10" screen.
If you've got any other questions let me know. I've tried to provide a brief overview.