I believe you can (we did this in November, albeit for just one day ahead of our check-in date), but I remember they told me that there is a limit on how far ahead of your WDW check-in you can activate your park tickets, if you've bought everything as a package. I want to say it was "up to 3 days" ahead, but I'd call WDW directly if I were you, to find out if this is still the case, and how it will work. For example, we had to go to WDW and get our tickets/MagicBands specially "activated" before we could use them, because, as it was explained to us, the Disney MDE ("My Disney Experience)" online system assumes you won't be using them until your check-in day. For the same reason, we couldn't make advance Fastpasses (not even at 30 days) for those days. MDE would only let us make Fastpasses for our anticipated check-in day at WDW, and the days thereafter (and we could do so at the 60-day mark, as onsite guests). The CM who activated our tickets when we arrived did offer to make Fastpasses for us immediately, from the available inventory for that day, and did so, so we could head right to a park without having to mess with the system ourselves.
For those reasons, you may wish to buy your tickets and room separately (unless you're getting a discount or special offer that requires a package booking), which, I believe, would save you the hassle of having to get your tickets activated on arrival at WDW, and would, for days that didn't already fall within your 60-day FP+ window as an onsite guest, allow you to make 30-day FP+. (But double-check on that when you call WDW.)