Please be aware with the the Sony H-20, the wide angle of the lens is really not wide angle at all. You are used to an 18mm lens which has a 35mm equivalent of 27mm, the Sony H-20 has a 35mm equivalent of 38mm which is huge and would limit most people who want to shoot landscapes, group shots especially indoor where you often can't back up to use a longer lens.
The mentioned Canon SX200 has a very similar coverage to the focal lengths you currently have.
It is worth pointing out that you are not going to get nearly the same level of quality with a point and shoot camera as you will get with your D70 but you will gain convenience of smaller form and no need to have additional lenses. Also due to the smaller sensors you can't do such creative shots where you have the background nicely out of focus etc.
Back to options to consider, I would look at cameras like the Panasonic FZ35 and the Canon SX20IS as it will give you the extra zoom you might want when shooting the marching band as I guess often you are not that close. The Panasonic has a bit better flash built in but the Canon will allow you to add an external flash at a later date which is a bonus.