No it is not a mosaic virus. Mosaic viruses will make your leaves deformed.That is just a normal pattern on some squash leaves.

Those bugs look like they could be aphids. If saw that many on a leaf I probably would have just cut it off too.

Oh and I see you have a nice looking pumpkin growing in the second picture.

I think you will be please with that plant, volunteers always seem to grow the best (for me at least).

I really appreciate your input. I was pretty worried, and to be honest, still am. I don't know much about growing pumpkins but I do know that aphids can do serious harm...right? I am so excited about the pumpkins that have started that I would be pretty upset if they got "sick" and died on me! A few of the back leaves have been effected by them but over all the plant looks good.