If you already have a Publication in a well respected journal you are already ahead of where most Peds and Psych residents will be at the end of their residencies.
If you want research, my advice is always to get started on clinical research. Bench work isn't going to get you anywhere unless you have a full year to do it. If you like Peds I have found NICU, PICU, and Peds Heme/Onc doctors usually can all direct you towards a project or two. Just cold call them and ask to do a chart review, or something similar. Peds isn't plastics/ortho where every gunner is banging on the door begging for a research project and a LOR, usually Peds attendings are ecstatic to mentor someone who is actually interested in their field.
Also don't wait for the summer, start now. Clinical research usually takes very few actual hours, but many, many months. Write an IRB, send to advisor, wait a month for edits. Get edits, submit to IRB, wait two months, get more edits. Complete Edits, approve IRB, spend 2-4 weekends actually doing the project, send to stats guy, wait two months. Get stats back, write up paper, send to advisor, wait two months for edits. Accept edits, send to journal, wait four months for comments. Get comments, send back, wait three months for acceptance. Accepted! Wait 6 months for publication. Just start now and you might get it done in time for the match.
I agree with the posters above that step 1 prep is going to be very low yield this far out from the test. Also I agree with the posters above about the Spanish thing if you're not fluent yet. Great investment.