You are not "inheriting" the firearms. Inheriting means you're getting them from someone who died, you're just receiving the guns as a gift. All interstate firearm transfers (sales, gifts) have to go through an FFL. Long guns can be transferred at an FFL in any state, while handguns have to be transferred by an FFL in the recipient's state of residence.
If they are all long guns, then go to an FFL in his state and have them transferred to you. File FA10s as "Registration" on them within 7 days of returning to MA. They must all be legal under the MA Assault Weapons Ban. Same with magazines (10 rounds or less if made after 1994).
Any handguns will have to be shipped to an FFL in MA and transferred to you there. The FFL with handle the FA10s in that case. Handguns need to be MA compliant and magazines must be AWB legal.
If you're going to have stuff sent to an FFL in MA, you need to arrange it with them ahead of time, and they will need to know what kind of handguns they are to ensure they are MA compliant. They will also tell you what their fees are, and whether they will accept shipments directly from you or only from another FFL.