As it is written, I think it is possible, but I would just like to be sure.

I am actually running Path of Cold. I just gave an XP award. Most of my players will also spend DM credits as 4 out of 5 active players have some. The last, @Lord Sessadore, doesn't, and Raiyek, his PC, is one of the two lowest lvl PC.

My party is likely to end with 4 Paragon Tier (lvl 13, 13, 12, 11) and 1 Heroic Tier (lvl 10) PCs.

I would like to spend come of my DM credit (probably 4 out of the 20) gained during this XP award to spend on Raiyek, so all the PCs in my adventure are within a 2 level gap and all Paragon.

Can I?