There are obviously some things to be very careful in terms of shopping for a deal, but that's also how higher valuations occur. And, if the acquiring company doesn't want to deal with it they can give you a "no-shop" offer that is higher, in addition to the breakup/no-deal fee.
*This "should" in addition to everything else above is just an opinion. I've only been in a company once that was acquired successfully and heard stories about other situations, so take it for what it's worth which might be nothing :-)
(PS, why can't I reply to the comment to my comment? I guess I don't comment enough to understand HN :-)
There's sometimes a timeout, to discourage rapid back-and-forth arguing.
even then, its not over till the cash is in your account.
I've seen friends' companies acquired without them ever seeing the full "acquisition price".
But you need to realize that just because you've been approached for acquisition and even if somebody tells you straight up "we want to acquire you", it sounds like you are far away from actually getting acquired. The road from casual interest to money in the bank is long and bumpy.
Unless you actually have a term-sheet in your inbox, you aren't in the position to make this decision right now.
The right tactical approach is for you to push hard on both fronts - push as hard as possible on fundraising as if you have no other option. And if you do want to consider an acquisition, start approach these companies and ask for term sheet.
If both go well, then you have a decision to make.. (and more leverage..)