Highload wallet doesnt use explicit seqno, it uses a short lived cache using a dictionary, and the key for each transaction is the query id.

So if you want to guarantee that the 100 transactions were sent successfully you should query your wallet adress using getTransactions API using a toncenter service (or others) and verify that the external transaction created a 100 output messages

As client software and the smart contract in question are two separate entities it would be better to actually verify that transaction was actually processed and the outgoing messages were created and submitted for processing.

What you should do is:

1). Create an external message for your highload wallet with the list of value transfers that need to be done. Get the hash of the external message or it's body.

2). Submit the message to the network.

3). Poll for the latest transactions from the Blockchain using your wallet account ID and match the transaction using the pre-generated hash.

4). Check that transaction has been executed successfully (exit code = 0 || 1) and make sure that outgoinng messages contain all of the required value transfers with the correct values.

This ensures that the transfers were actually made. However, if you need to make sure that they were in fact delivered (and not bounced back) you will need to query each individual destination account and check for incoming transactions by matching them using the outgoing message hashes.