Justin, I am a school teacher so everytime I make the trip to Disneyland it’s 99% of the time in June. We’ve never had a problem and love it! If the crowds get bad it’s usually after 11am so make sure you take advantage of those early morning entries if you can & do a lot of the major attractions first.
I don’t get there until the end of June and it is always HOT but managable. It’s usually between the hours of noon-4pm where we noticed the killer heat. So if you’re not a fan of the blazin’ sun just use the late afternoon for nap or pool time.
I’ve stayed at the Disneyland Hotel & the Grand Californian several times and love both. I prefer the Grand Californian though 'cause it has a private entrance into the California Adventure Park, beautiful & peaceful rooms, a nice pool, etc. I love it there.