Proper job search etiquette?

[?????]

I'm graduating this May and am in process of looking for a full time job. I just got the news that the company that i interned with in the past is interested in giving me an offer very soon. I loved working for that company, and I got excellent experience and very good feedback at the exit interview. There are several other companies that are interested in interviewing me, and I would like to see what other offers I can get, but I do not want to lose a chance with the first company.
Originally I didn't expect that i would get an offer right away, and I was hoping to use my mangers as a reference for other companies that i was applying for, but now that I know that they want me to work for them, I don't know how to ask without making it seem like I'm not interested.
Ultimately I like the company and want to work for them, but on the other side I haven't seen anything else and want to explore my options.

What is the proper professional way to deal with this situation?
Can I still ask them to be my reference?