More advice needed - contacting researchers

[glasscandie]

So in looking for a summer research position, I contacted a professor who said that he would probably be able to give me an unpaid position in his lab as a research assistant, and to e-mail him in March. Great. Now, I'm beginning to contact professors that I'm interested in working with for graduate school, and the researcher who offered me the position is on my list for that school. Should I contact him, as I am contacting other researchers, or should I wait until over the summer when I'm (hopefully) working in his lab?