If you want to seize this opportunity, do so. Timing is huge.
A submission to one publisher isn't going to sink your chances with an agent if you decide to query agents. (I wouldn't try more than that, though.) Especially if it's a smaller publisher that agents might not try anyway, because for them these houses are usually much more work for much less pay.
Whether to query agents or go directly to publishers is a bigger-picture, career-trajectory question. It depends what path you want to follow. An agent on your side can open many more publisher doors for you, which helps so much because this is a numbers game, in addition to everything else an agent can do for you. But if the best markets for the type of work you do are smaller publishers that might have a certain niche, you might do okay on your own. It is easier, though, to make a go of it without an agent if you already have a number of good editor contacts of your own.