Help! Accepted to 2 PhD programs, one announces funding AFTER 4/15

[CNM2phd]

Hi all, 

I have been admitted to 2 PhD programs. My top choice doesn't adhere to the 4/15 deadline and won't be announcing scholarships/assistantships until "early May". My second choice has the 4/15 deadline but has offered a guaranteed TAship with full scholarship. I thought about asking for an extension from my second choice, but I worry about negatively impacting the relationship with them and don't even have a precise date to ask for. Would an extension even be an option in your opinion?

I feel like the best approach is to email my top choice, explain the situation, and ask if they're able to offer an assistantship before 4/15. Thoughts? Any advice on wording this or other approaches? Thanks!!