Aliyot Ordering for Bar Mitzvah

Our nephew will be having his bar mitzvah on Rosh Chodesh Chanukah which has four aliyot. The preference is to give two Leviim and two Yisraelim aliyot (with Revii going to the bar mitzvah boy who is a Yisrael). Assuming there is no Cohen present (they are all willing to step out) is it permissible to call up two Leviim back to back? If not, does putting a Yisrael in between the two Leviim solve any problem? If one of the foregoing options is OK, does the gabbai need to say anything special (af al pi?) for calling the second Levi? Thank you.

Mazal tov on the bar mitzvah.

In the case when there are no cohanim it would be optimal to have an yisrael between the 2 leviim. As this is a Halacha mefurrshet there is no need for the gabbai to announce anything.